Revealing mistake: When Abby and Jen are drinking on the dock, Abby suddenly falls into the ocean and drowns. Just as they show a close-up of Abby falling about to hit the water, you can tell it's a stunt person. Monica Keena is a fairly short actress, and the stunt person is noticably taller with longer legs. Also, Abby had been wearing a very decorated black and silver skirt while on the dock. But the person about to hit the water appears to be wearing dark clothing without any silver or glitter.
Valentine's Day Massacre - S3-E14
Revealing mistake: When Jen goes to visit Henry at the hospital, he is eating a small individual-sized Jello. There is another identical Jello on the same tray, in front of Jen when she sits down to talk to Henry. You can see that the corner of the Jello lid has already been pulled up rather noticeably. This is probably to make it easier for Michelle Williams, the actress to be able to open the Jello quickly during her scene.
Revealing mistake: When Joey and Pacey are talking in the car as Pacey drives them to the Train Station, you can see at least 3 lanes full of cars and a great deal of traffic behind them. But when Pacey suddenly turns right, off the main road and into the entrance to the Train Station; you can see that suddenly the main road he has just turned off of is almost completely empty of any traffic in either direction, except a truck that drives by at the last minute. It also appears to be a smaller road. Apparently the scenes with their dialogue in the car were shot with background video that wasn't the actual location.
Revealing mistake: During this scene Joey is running from the wedding to find Pacey. There is a young couple dressed in light blue, standing on the left side of the scene. The man appears to turn his head and see Katie Holmes running towards them, and puts his arm around the woman next to him and directs her across the grass over to the right. They both sort of suddenly run over to the right in order to clear the way for Katie to keep running straight through the area. It's obvious they moved intentionally so as to get out of her way, knowing the actress was about to run by them. (00:34:20)
Coming Home - S4-E1
Revealing mistake: This scene of Dawson and Joey in the parking lot of the "Dive-In" was not really filmed in the same location. The show only had the location of the "Dive-In" for a limited time, and had to film all other related scenes in the parking lot of the studio in Wilmington, NC. Any scenes that don't show water in the background; and are just palm trees, lighting etc. were actually shot several weeks later in the parking lot, which was recreated to be part of the beach at the "Dive-In". (00:33:30)
Coming Home - S4-E1
Revealing mistake: In the first scene, Pacey says something like see I think we should probably drop anchor here, have a bite to eat (and other things)... As he's walking around the boat, the camera shifts over and you can see two ropes that indicate the boat is already anchored or docked to something.
A Family Way - S4-E5
Revealing mistake: During the scene when Dawson and Gretchen are talking on the bridge, two couples walk by in the background. An older couple passes from left to right, and a younger couple walks from right to left. The younger couple is a woman with blonde, curly hair wearing a green top and beige/white skirt, and a guy wearing a green or blue top and white pants. During the same scene, the same younger couple again walks by in the background from right to left two more times. Then the older couple walks by again from left to right. Then one final time, the younger couple walks by yet again for a fourth time from right to left. Guess they were using the extras a lot that day. (00:27:15 - 00:28:50)
Revealing mistake: When Dawson arrives home after his evening with Gretchen and friends, his Mother is seated on the couch waiting up for him. As she talks to him, she stretches back, still seated on the couch; and you can see on her stomach the outlines of the padding she is wearing to make her appear pregnant when she really isn't. (00:35:25)
Mind Games - S4-E16
Revealing mistake: When Jen and Jack are having coffee at the coffee shop, Jen walks outside and turns to bang on the outside window of the store to get Jack's attention. When she hits the window, you can tell it isn't a real window made of glass. It's obviously some sort of plastic, as it flexes too easily and moves too much to be a real store window. This was probably done to make the window safer for the actors during this scene.
Revealing mistake: When Doug stops Pacey on the street to talk to him, Pacey turns to face Doug (and the camera). You can see at this point, the microphone sticking out from Pacey's upper shirt. (00:04:25)
Revealing mistake: When Grams is in the Kitchen with Jen and Jack, her sweater isn't buttoned right. When she walks close to the table you can see that the bottom edges of the front of the sweater don't match. It appears to be about one button off-one side is higher than the other. (00:26:35)
Revealing mistake: When Pacey and Audrey are in bed at Pacey's boss' house, there is a shot where Pacey is lying back down beside Audrey. He appears to be wearing a tank-top style t-shirt, and loose boxers. But you can see that he is actually wearing tighter white briefs UNDER the boxers, obviously so as not to be too revealing. Therefore the boxers aren't really his underwear. (00:06:10)
The Song Remains the Same (2) - S6-E2
Revealing mistake: When Jen and CJ are talking at Boston Bay University, and CJ mentions 'The Stand'; Jen suddenly gets up to leave thinking he is referring to religion. As she turns to walk away; you can see for a brief moment the real tattoo on the lower back of Michelle Williams, in the slight gap between her shirt and pants.
Revealing mistake: When Joey and Pacey are playing Battleship, there are a few close-ups showing their game screens. Although you can see several push-pins in each screen, signifying the areas of the game they have tried; there are no actual ships visible. It looks like they are playing the game with only the push-pins, and not any actual battleships.
That Was Then (aka Before and After) - S6-E16
Revealing mistake: In the very beginning of the episode, Pacey is watching TV and gets up to look out the window towards Hell's Kitchen. As he moves back from the window, he accidently bumps the kitchen counter/cabinets. An entire section of 'counter/cabinet' moves noticeably; revealing it to be a cheap, flimsily-built fake kitchen counter/cabinet instead of a more substantial, real one. This was obviously just part of a set.
Revealing mistake: When Joey hands the reporter the cup of coffee in Pacey's office, you can tell the cup is empty. It tilts to one side, and is behaving as if very light without any fluid in it. Joey pretends to pour cream into the cup, implying there is already coffee inside. But the way the cup tilts in the reporter's hand, it's obvious it's actually empty.
Revealing mistake: When Pacey and Rich are physically fighting in the office, there is a quick shot of a person who is supposed to be Pacey leaning forward over Rich and hitting him. However, if you look closely you can see that the hair on this person although dark brown, appears much longer and curlier than Pacey's current hairstyle. Also-just before that shot ends, you can see the longer hair swing away from his neck loosely on the right side. The next shot of Pacey shows his shorter haircut, so I believe the longer hair was actually a stunt man substituting for Pacey in a risky, physical scene. (00:40:00)
Revealing mistake: Towards the end of this episode, Joey comes back to her Dorm room and spots the envelope Eddie left for her. You can see her name written on the outside of the envelope, and it's supposed to be Eddie's handwriting. But in fact, it looks exactly like Joey's handwriting as shown throughout the series. When Joey is talking earlier to Professor Hetson and he hands her the exam booklet with her writing on the front, it's the same style of handwriting. During other episodes, we see what is supposed to be Joey's own writing (ie: her note to Dawson during the Series Finale that she leaves on his bed) which is also very similar. So in fact, what is supposed to be Eddie's handwriting on the note to Joey really looks more like Joey's handwriting, or the same person who really does the writing for Joey's character.
Goodbye, Yellow Brick Road - S6-E21
Revealing mistake: Watch Busy Phillips' hand in the bar scene where Audrey sings - she's very obviously not playing that guitar.
All Good Things... (1) - S6-E23
Revealing mistake: During the scene when Jen is telling Jack about her illness in the hospital room, she asks him to get into bed with her and talk. As he does that, Jen lifts her right arm to allow room for him. There is a tube attached to her right arm at the inside of her elbow, that is supposed to be going into an artery. But you can see that the end of the tube is actually pointing the opposite way, and sticking up through the tape pointing towards us. Obviously this was because they couldn't actually insert the tube into Michelle's arm for the scene.
Answer: It's only explained once in the series. Jack says to Andie "I tried to start kindergarten without you", meaning Andie was smart enough to start school early.