Continuity mistake: When Marge runs back to the kitchen to retrieve the wedding video, the house is ablaze. In the next shot, when the mob is carrying the car away, there are no flames visible in the house.
Continuity mistake: In front of Krusty Burger, when Lou carries a naked Bart to the sign post, the post is embedded directly in the concrete walkway slab, just beside the left corner of the patch of grass. Once Bart is cuffed, the sign post has actually moved down about 4 feet, and is also now embedded directly in the grass at the right corner. In following shots, it's at the left corner of the grass and then right again.
Continuity mistake: In the cinema, when Homer tells everyone how boring this is, behind Bart, Lisa, Maggie and Marge sits Otto, Kirk van Houten and Barny, but in the next scene behind them sits Otto, Jasper, Kirk van Houten and Moleman.
Continuity mistake: When President Schwarzenegger tells Russ Cargill he will have to go back to making family movies, there is a "Diaper Genie" promo poster on the Oval Office wall and on the immediate left of President Schwarzenegger's desk. But the promo poster disappears and the walls of the Oval Office become further from the desk in the next long shots.
Continuity mistake: When Homer and Bart are fixing the roof (near the beginning) there is no tree near Ned Flander's house. Later on Bart is on a tree next to Ned's house talking to Ned Flanders.
Continuity mistake: When Maggie does her disappearing act through the sinkhole, and Marge rushes to get Homer, the wooden porch swing is directly in front of the window, with its top beam as high as the top of the window. When Homer says, "This dome can play tricks on you," note the door and window behind Marge, because the swing is now gone.
Continuity mistake: When a naked Bart is cuffed to the sign post, beyond the grass behind him is concrete walkway then the curb. Then when Homer steps out of the car, the grass goes right up to the curb's edge, but when Bart asks about pants, the walkway is back again between the grass and curb.
Other mistake: On the close-up shot of the "Doomsday Clock" with "Sponsored by TIMEX" underneath, the clock is counting up from 1:33 to 1:34, rather than down.
Continuity mistake: In the scene where Lisa's boyfriend is trying to play "Lisa's song" from the other side of the glass, at first the guitar has an f-hole, and in the next shot of him, it's a solid body guitar.
Continuity mistake: When Marge is reconstructing Grampa's prophecy with magnets on the fridge, she moves the magnet saying" eyes" up a few inches to complete a sentence. When the shot changes to a wider angle, the magnet is back where it was before she moved it.
Continuity mistake: In the motel room, the poster of Alaska is not reflected in the mirror behind Marge. You can only see the little lamps next to the bed.
Continuity mistake: In the mob scene the boyfriend of Milhouse's mother Luann is seen twice - he's somewhere in the middle, and also at the back of the mob.
Continuity mistake: When Homer is grooming Spider Pig he is in Bart's room and it's on the end of the house because you can see the corner of the house, then he walks out of the room and goes in another room but that room is on the end of the house too, you can tell it's a different room by looking in the background so it doesn't make sense that both rooms are in the same place.
Continuity mistake: When Grandpa is freaking out in church, he says, "twisted tail" while kneeling with his hands cupped, "a thousand eyes" leaning up against a pew, and "trapped forever" standing up and spinning. On Comic Book Guy's cell phone video he says all of these on the floor rolling around. He's also saying it faster on the cell phone video.
Continuity mistake: During Bart's flashback of him and Homer fishing, Homer drops the bug zapper into the lake. Dozens of fish come floating to the surface all over the lake. After the shot where Homer scoops up a fish and is zapped for it, there's a reverse-angle shot of Bart with no dead fish in the lake around him.
Continuity mistake: When Chief Wiggum orders his men to open fire on the dome, and the bullets ricochet back, the officer standing farthest from Wiggum is wearing blue gloves on both hands in the overhead side shot, and the other officers are not wearing gloves. However, in the shot facing them, the officer kneeling farthest from Wiggum is the one wearing blue gloves, and now all the others are barehanded.
Continuity mistake: After Lou shoots at Bart's skateboard, before Bart flies past the truck's windshield, when we see Krusty Burger across the street (note the post and triple window), the road surface has double solid yellow lines. The double lines can also be seen when Lou scrapes Bart off the window. However, when Bart is handcuffed to the post, that same road now has single broken lines.
Continuity mistake: When Lisa sees Milhouse near the end, the door on his house hangs askew from the right door jamb and there is nothing above it. However, after Colin shows up, in the next shot when Lisa jumps up, the door now hangs askew from the left door jamb and there is wiring hanging above it (from the broken light fixture). Also note that the roof is much lower. Additionally, Lisa's position when talking to Colin changes - first they're standing to the left of the house, then to the right of it, then in front of the stairs at the center.
Continuity mistake: When the Simpsons first get to the spherical cage at the carnival, the truck is parked with its front facing forward and its back end facing away, behind the ride. However, when Homer gets in and drives away, the truck has turned about 90°, with its back end now facing the ride perfectly.
Continuity mistake: When the angry mob breaks down the front door of the house, the door knob is on the right side of the fallen door, at Chief Wiggum's feet. However, when Maggie breaks her bottle and thrusts it forward, in the next shot as Mr. Teeny turns and runs away, the doorknob is on the left side of the door, at Bumblebee Man's feet.
Continuity mistake: After Homer nailed the bedroom door shut and then mimicked the sound of a chainsaw, when the hands of the angry mob push through the holes again, we see Marge and Lisa sitting at the edge of the bed where the bed's tall footboard should be. The footboard is back when Spider Pig pushes the plank off the windowsill.
Continuity mistake: When Marge and Homer are watching the news about the silo found in the lake, the TV sits on the dresser in front of their bed. The TV has vanished when Lisa runs into the bedroom, and when Marge tells Homer to go out, face the mob and apologize for what he did, the rest of the wall is visible, sans TV.
Continuity mistake: When Bart walks into Krusty Burger, in the overhead shot the trash receptacle that's beside the door has a plain, flat top with nothing atop it. However, in the following shots the top of that trash receptacle has changed, it now has two raised side lips, and there are also two trays on it. Its height compared to the window behind it drastically changes as well.
Continuity mistake: In the exterior shot of the Simpson house, before showing Homer and Marge watching the news about the silo being found in the lake, we see the side window (facing the Flanders' house, from which they escape later) is a horizontal sliding window. However, from inside the bedroom and also when they are escaping, that same window has changed to a vertical sliding window.
Continuity mistake: Right before Homer yells out of his bedroom window, when the shot moves forward, passing through the large angry mob, we see the mob walking down the street which is perpendicular to the front of the Simpson house (not the street in front, that runs parallel to his house). The problem is that after the dome was placed, when Homer screamed in the backyard, there was an overhead shot that zoomed out and we saw there are homes across the street from his house, no perpendicular street.
Continuity mistake: After the dome is placed, when the Simpson family runs out the back door of the house and Homer shouts, there is only one window on the second floor, above the back door. There should be two windows. The light fixture on the wall beside the door is also gone in some shots.
Continuity mistake: When Marge brings Homer to see Maggie outside the dome, but she's not there, he soon starts cheering and in the dome's reflection he raises his right arm which means it's his left arm that is actually raised, but when it cuts to Marge and Homer (in the view from outside the dome) it's his right arm that's raised in a cheer.
Continuity mistake: With the second set of options spread across the desk, when Cargill starts manipulating the President's option choice, there is a blank wall to the President's left (the wall faces the viewers). Also note that in this shot the table behind the President (with framed photos) is gone. When Cargill walks away from the President holding 'option 4', that blank wall now has a built-in bookcase, a table and chair.
Continuity mistake: There is a blue Presidential flag behind the President, with windows on both sides of that blue flag, but after viewing the security camera footage of domed Springfield, the window on the far end has become a solid wall. That window returns when Cargill influences the President's choice of options.
Continuity mistake: When Russ Cargill spreads the second set of the five options across the President's desk, the Oval Office background is actually backwards - note the ship painting over the fireplace and pictures on the wall. The background keeps flipping between being backwards and the correct way until 'option 4' is chosen.
Continuity mistake: When Russ Cargill provides the President with the first set of five options and spreads them across the desk, the handle on the mutated squirrel tank is perpendicular to the president, but in the next shot the handle has flipped around and is now parallel to the president.
Continuity mistake: After Russ Cargill goes through the eye security system, in the overhead shot as he enters the Oval Office, we see the Seal of the President (on the rug) centered between the two couches, and there are two red chairs behind each of the couches. However, when Cargill holds up the tank with the mutated squirrel, the large round Seal is off to the side of the couches and one of the chairs is gone from behind the couch.
Continuity mistake: When Lou scrapes Bart off Krusty Burger's triple window, Lou is pushing Bart forward in front of him, so Bart should have fallen on the ground somewhere to the front/side of Lou. However, in the next shot Bart is lying on the ground about 20-30 ft behind where Lou had been standing, on the grass that's in front of the door.
Continuity mistake: When Lisa goes door-to-door with the petition, the door on Milhouse's house has two grooved panels, a tall, 12-panel window, a light fixture above the door, and there's a tree between it and the blue house next door. When Lisa sees Colin and Milhouse again near the end, some of the features of the house have changed - unrelated to the damage Springfield's homes have suffered. The door now has three grooved panels and no mail slot, the window is much shorter, and the light fixture above the door is gone, with no hole in the wall if it had been broken off. The tree between the house and the blue house next door has changed position on the grass as well.
Continuity mistake: When Nelson punches Milhouse in the stomach, there is a hose hanging below the window attached to a spigot, and the front door has two grooved panels on it, but when the dome approaches and Milhouse swallows his inhaler, the door is flat and smooth, and the hose, its holder and spigot have vanished and been replaced with a bush.
Continuity mistake: When Homer dumps the silo in the lake, there are the words "Pig Crap" on the front and there is no writing on the back. However, when Lou and Eddie find the silo later in the movie, the "Pig Crap" words are there, but the words saying "Return To Homer Simpson, No Reward" has appeared out of nowhere.
Continuity mistake: When Homer leaves the bar Eski-Moes (in Alaska), he catches hold of a truck, which propels him up the hill in front of his cabin. However, he runs outside a few minutes later and floats away on the heart-shaped iceberg, which has suddenly appeared on a lake that was never there before. The road that the truck was on earlier is gone.
Continuity mistake: The Simpsons enter a motel (Red Rash Inn) to hide, and it's clear from the outside that the building is only one story high. But when Homer flings back the curtains to reveal the buildings and billboards, it appears that the motel room is located on a much higher floor, since the view seems to be level with the building tops.
Continuity mistake: In the scene where they are climbing the rope to escape the dome, the hole seems to be very wide. Yet when Homer is on top of the dome the hole is very small.
Factual error: In the scene where the angry mob is attacking the Simpsons in the tree house, Grandpa Simpson is shown aiming a double-barrel shotgun, which he then pumps to ready it for firing. There's no such thing as a double-barrel pump-action shotgun.
Continuity mistake: The bottle of ink and quill on Mr. Burns' desk disappear for one shot. This happens when Apu, Chief Wiggum and Dr Hibbert are asking for some electricity.
Continuity mistake: In the scene where the newscast (Day 37) is being watched on the TV at Moe's, in the first shot of the TV there is a dart in the roof, but in the long shot the dart is no longer in the roof.
Continuity mistake: Cletus is shown on a roof attempting to distract Cargill as the group was trying to climb the rope, and is still there when Cargill turns off the transmission between Springfield and Cargill. Yet when Homer says "I can't do anything right" a few minutes, Cletus is suddenly shown in the background behind Homer.
Continuity mistake: When Cletus goes to distract Cargill, a crowd of Springfield citizens go to place the KBBL news tower next to the rope so they can climb up it. They are all on the ground when Cletus starts talking to him. Cletus then says "Look what I can do with my thumb" and the crowd is suddenly half way up the rope with no time to do so.
Continuity mistake: When Homer puts the video in the VCR player, as Marge says "Homer", outside the window shows a dark sky in the background. Marge then talks for a bit and the shot returns to Homer saying "Way back." Outside the window suddenly shows a background that is partially brighter and raining.
Audio problem: When Marge, Bart, Lisa and Maggie are trying to convince Homer to save Springfield, after Homer says "That is the stupidest thing I ever heard", Marge says "Homer Simpson!" then Lisa says "We're saving Springfield." When Lisa says "Springfield", her mouth reads something totally different.
Continuity mistake: After the Alcoholics Anonymous meeting runs out of the dome, Barney starts yelling and a huge crowd is visible behind him. Bumblebee Man is standing a few meters away from Barney on the end of a row. Next shot, Otto and Moe have suddenly appeared next to him as well as a huge crowd.
Continuity mistake: When the Alcoholics Anonymous run out of the church, Barney yells out "I can't take another minute in this dome!" and charges towards the dome. In the overview shot, the church is directly behind Barney. In the following shot that shows Barney hitting the dome, the background has changed completely. The church is no longer there and two houses have suddenly appeared.
Continuity mistake: When the two deer enter through the cabin window to help Homer and Marge, a trail of snow is visible behind them and in front of the window. In an instant close-up of the smaller deer, half of the snow has instantly melted and vanished. Then all the water has vanished and it's just snow. Then a few shots later, the snow vanishes completely.
Continuity mistake: When the Simpsons are at the gas station, Marge congratulates Bart on being sober for 24 hours. The Buzz Cola can next to Bart has the logo facing front ways. Bart then aims his slingshot which cuts to a shot from behind them and the Buzz Cola logo on the can is still facing front ways, despite the angle change.
Continuity mistake: When Bart and Ned find the mutated squirrel, two EPA workers find the creature. When the female worker says "Environmental Protection Agency" after Ned asks who they are, the squirrel is standing on a rock with nothing under it. In the next shot, there is suddenly something under it for the EPA worker to contain it with.
Continuity mistake: When Homer returns home with Spider-Pig, Maggie's high chair is positioned to be facing the archway between the kitchen and living room. A few seconds later, after Marge realises Spider-Pig is the twisted tail, Marge says "I believe what happened in church was a warning about precisely this" and Maggie's high chair is suddenly positioned to face the fridge.
Continuity mistake: After Homer decides to bring Spider-Pig home with him, the scene cuts to Maggie playing the game "Baby Blast." On the back of the game console is the disc with the words "Baby Blast" written on it. As Grandpa says "I'm pretty sure a thousand is a number" a few seconds later, the words "Baby Blast" have vanished from the disc.
Continuity mistake: When they film Krusty's advert in Krusty Burger, "Action" is said by the director and the only things shown are Krusty, the pig and the table the pig is standing on. Krusty then starts talking whilst filming and picks up the burger known as The Clogger. This burger was never visible during the previous shot as the director said "action".
Continuity mistake: After the Simpsons have left the church with Grandpa wrapped in the rug. Homer asks "Who wants waffles?" In this shot, there is a line along the left side of the rug, showing us where the end of the rug is located. A few shots later, as Homer says "I rest my case", the line showing us the edge of the rug has vanished.
Continuity mistake: When the crowd throws food and drinks at Green Day's barge, the first overview shot shows various items landing on the barge. A few shots later then shows us another overview shot of the barge, only the amount of items has decreased. Then as one of the members says, "Gentlemen, it's been an honour playing with you tonight" and they take out their violins, all of the items on the barge have vanished.
Continuity mistake: When the Green Day singer points his microphone to the crowd and the crowd sings the rest of the song, note the front of the crowd has nothing in their hands. After the singer says "We've been playing for three and a half hours. Now we'd like a minute of your time to say something about the environment", the shot returns to the crowd and everyone on the front row suddenly has a drink in their hands.
Continuity mistake: After Lou chains Bart to the pole with his cuffs, the next shot shows he has a new pair, when he didn't in the last shot.
Continuity mistake: In the scene where Mayor Quimby says "To make sure this wall is completely idiot-proof...Cletus", in a far shot, Cletus comes walking up with his hands empty. It then cuts to a close up and now you can see the opossum tail in Cletus' right hand. There is no time for him to have grabbed it from anywhere.
Continuity mistake: Homer leaves Eski-Moe's with nothing in his hand. Then he grabs onto the back of a truck with still nothing in his hand. Homer lets go of the truck and zooms to the house and there's still nothing in his hand. But when he opens the door, there's suddenly a bouquet of flowers in his hand.
Continuity mistake: When the Simpsons are driving to Alaska, Homer puts the poster of Alaska on the window. Marge then removes the poster and we see the van is going out of control. In the next shot that shows them screaming, we can see they are driving totally normally judging by the view from the back window.
Continuity mistake: When Maggie jumps into the sink hole whilst the mob are invading, Drederick Tatum (the Mike Tyson parody character) is seen standing directly in front of the dome. But after Marge, Bart and Lisa have jumped into the sink hole and it cuts to a wide shot, Drederick Tatum is seen a lot further away from the sink hole than he was previously - look closely to the right of screen in the wide shot, that's where Tatum is.
Continuity mistake: When the car is being taken into the garden, Bart says "Up here." At this point, one of Fat Tony's assistants is seen lifting the rear end of the car at the left hand end. But if you look in the shot where the car is lifted up, you can see there is no sign of Fat Tony's assistant.
Continuity mistake: When Bart is handcuffed to the lamp post, Nelson is stood in front of Bart laughing at him, then Nelson's mother walks into shot and she starts laughing at him too. There are also 4 other people standing around the lamp post too. But when Homer arrives in shot (a second later), Nelson, his mother and the 4 other people have magically disappeared.
Other mistake: When Homer falls through the roof into the house we see Grandpa sitting somewhere other than the ground floor or the second floor. The problem is the Simpsons' house has an attic on top of the second floor and below the roof. The length of the attic's floor and the house around it are totally the same, so really what we should have seen was the attic, not Grandpa sitting somewhere.
Continuity mistake: When Homer is doing his chores, he covers the sink hole with the sand box and the sand starts sinking too. About a minute later as Bart is hanging off the roof just as Homer falls into the house, Maggie is seen in the background in the sand box, but there is no sign of the sand sinking.
Continuity mistake: At the end when everyone is cheering at Homer and Homer notices Marge, Lenny and Carl are in three places at once. First, just as Homer starts his bike to get Marge, Lenny and Carl are right behind him. Second, just after Homer carries Marge on to the motorbike Lenny and Carl are behind Homer without enough time to move. Third, just as Homer and Marge drive off in the motorbike, Lenny and Carl are now in front of Homer without enough time to move.
Revealing mistake: When Grandpa is being rolled out of the church, everyone is looking at him. As this happens, look closely at the Squeaky Voiced Teen sitting next to Hans Moleman on the right hand side of the church. As he turns his head around you'll see his eyes disappear as he stops turning his head.
Continuity mistake: When Bart and Lisa are looking at the cabin from a hill, the cabin only has a shallow incline to the water, but in a later shot there's a significant slope.
Continuity mistake: When Bart skateboards to Krusty Burger naked, he passes Agnes Skinner in the middle of town. On the left side of the screen is Mr. Largo, the school music teacher. A few shots later, when Bart approaches KB, Mr. Largo is seen walking down the sidewalk. There is no way he could have caught up and passed Bart in that time span. Not only that, but he and Bart are headed in completely different directions.
Continuity mistake: When Homer is forced into the house by Bart and Lisa's avalanche, it is broad daylight, but seconds later he is with Marge in the bedroom and it is dark outside. It is not snow surrounding the house, because the animals come in through the windows.
Continuity mistake: In a scene Milhouse comes out of a house there is nothing in the yard, a long time passes, nearly ten minutes, Nelson comes over and there is a large rock in the yard.
Continuity mistake: When the family are in Alaska, Homer comes in with logs and Bart claps his hands to get snow on him. When Homer says Lisa should clap too, his hair changes.
Continuity mistake: The door to Homer's cabin in Alaska changes positions, from facing the street when he comes home from the bar to facing over a cliff when he decides to follow Marge and the kids back to Springfield.
Audio problem: After the mob walks away from the wreckage of the Simpsons house, Colin then knocks on the dome glass and a knocking sound is heard. Colin begins to play a song on his guitar and then the sound of the guitar can't be heard, despite the fact that we just heard him knock on the glass.
Continuity mistake: When Green Day finishes, in one shot the dice on the drums are gone, but the next shot, they are back on the drums.
Plot hole: There are two cars driving behind the EPA truck containing Marge, Bart, Lisa and Maggie. But when Homer uses the bulldozer to try and break the family out the truck, the two cars behind the truck don't even realize for some strange reason that a bulldozer is trying to destroy the truck. There's no way they couldn't have not seen the bulldozer since they were just behind it.
Continuity mistake: When the mob approaches Homer's house, it is undamaged. However, a few seconds later when everyone is out of the house, it is suddenly ablaze, and it is clear that it's falling apart. But when the sink hole sucks the house in a few minutes later it is undamaged, and no evidence of a fire is visible.
Continuity mistake: When Marge and Homer are watching the news about the silo being found, the '6' on Kent Brockman's microphone keeps getting smaller, the color of his belt buckle changes and the landscape in the background changes.
Continuity mistake: When Bart is chained to the post, a large piece of grass used to cover him appears from nowhere. The post also changes places from the sidewalk to the grass.
Continuity mistake: Near the end of the movie Bart and Homer are on the roof. Homer hammers the nail into the roof then stands and the shingles are nailed to his leg, however, you can see that he did not nail it to his leg.
Continuity mistake: When Homer is dressed as General Marriot Suites he's wearing white gloves but after he punches the guard the gloves have vanished.
Deliberate mistake: For the car to be carried by the angry Springfieldians, there would need to be a big jump between the ground and the car, but from the car view there is no sign of that.
Continuity mistake: In the scene where everyone is climbing the rope to get on the top of the dome, Homer should already be at the top, but when the camera points to the top of the dome, he does not appear there. The next scene shows him back at the top of the dome again.
Continuity mistake: After Grandpa goes nuts in the church, they go to the car. You can see that Homer has a seat belt on, but when Marge gets out he does not.
Continuity mistake: When Abe goes nuts in church, Comic Book Guy gets his phone to record him. When it cuts to Abe, Comic Book Guy is not holding his cellphone. However when the family roll Abe out of the church, Comic Book Guy is holding his phone again.
Continuity mistake: When the family move to Alaska, the door to their cabin opens to the left (looking at it from the inside) when Homer escapes from Bart and Lisa's "avalanche". But later in the film it opens to the right (from the inside).
Continuity mistake: When the wall is put up around the lake it is built right next to it, but when Homer dumps the silo the wall's much further away from the water.
Continuity mistake: When the Simpsons see the nooses in their backyard, you see Jimbo and Kearney put a pacifier on Maggie's noose, but in the next shot where you can see the nooses, the pacifier is gone.
Continuity mistake: When Homer and Bart are on the motorcycle trying to get rid of the bomb, the bomb slips out of Bart's grip. When he's hanging onto his father's shirt, Bart first grips the bomb's handle with his palm and fingers facing the front of the bomb, with the clock. Then when he's hanging onto his father's hair, Bart's hand has flipped around and he's now gripping the bomb's handle with his palm and fingers facing the back of the bomb. Something to look out for is the shot just before the close-up of Chief Wiggum, because as Bart raises his arm the bomb actually flips over in his hand while we're watching. Quite impossible.
Continuity mistake: At the gas station market, when Bart puts the can of soda pop on the counter, we see the yellow label on the glass beef jerky jar, facing away from Bart. When Marge points to the beef jerky its label has vanished, then when the clerk points to the similar looking family the label is back.
Continuity mistake: After Homer and Marge watch the news about the silo found in the lake, when Homer walks to the window we see that there are two blue panel drapes with tiebacks on the left and right side of the sliding window. However, when Homer shouts at the mob in the exterior shot, there is also another blue panel hanging down at the center of the sliding window, and the side panels are hanging straight down, without the two tiebacks.
Continuity mistake: When Homer is driving toward the small Alaskan booth, right beside the booth there is a tall flagpole with two raised flags, but when they leave the flagpole has vanished, though it should be seen in this shot since it's on the same little 'island' as the booth. Also note that the snow on the booth and island has vanished.
Continuity mistake: After the book knocks over the AA meeting's coffee machine, when the group of people run out of the church, the ground in front of its doors is flat and leads straight to the walkway. Additionally, there is a second large area of grass between the sidewalk and the street, and the large cross at the front is gone. However, in previous and following shots there are stairs at the front of the church, and the area of grass only between the church and sidewalk/street.
Continuity mistake: When Russ Cargill holds up the tank with the mutated squirrel to the eye security system on the wall, there is a square piece under the handle to secure it to the top. However, when Cargill holds the tank up to the President that square has vanished and it's just the handle. Then when the President is face-to-face with it, a bar has appeared between the two sides of the handle.
Continuity mistake: When Lou shoots at the skateboard Bart goes flying in the air, and in the next shot (before he flies past the truck's windshield) we see Krusty Burger across the street (note the triple window and post), and there is a tall, long bush between the street and Krusty Burger. That bush vanishes in the following shots.
Factual error: Marge, Bart, Lisa, and Maggie Simpson take the train from Alaska to Seattle, Wash. (The train shown in Alaska, is the exact same one that arrives in Seattle). This is not possible as there is no train, (passenger or freight), that links Alaska to the southern 48 states, including Seattle, Wash. Homer Simpson does not take the train to the southern 48 states.
Continuity mistake: During the bike stunt at the end, Homer's hair flows in some shots, but is completely rigid in others.