Continuity mistake: When Sam is in his bedroom, after he finds the Cube sliver it falls and dramatically burns a hole through the floor into the kitchen. But Sam's bedroom is over the living room (there is nothing on the ground floor below Sam's elevated bathroom, and in the first movie Jazz hides in this open space), and the kitchen is actually located between the den and dining room, at the other end of the house. If they were to follow the actual floor plan of the house, the Cube sliver would have landed in the area of the piano in the living room, but where would the fun have been in that?
Continuity mistake: While Mikaela and Sam are on the phone with each other (after the failed webchat date the night before), when Wheelie starts reaching up for the safe's combination lock in the first shot, there are no mouse traps on the floor near the short stool to his left, nor are there any cigar boxes. However, in the next shot two mouse traps (a snap trap with cheese bait and a glue trap) and two cigar boxes have all suddenly appeared. Wheelie proceeds to step on the two traps and then stands on the two boxes to reach the combination lock.
Continuity mistake: After Mikaela throws the metal box at Alice and breaks the window, when Sam runs out of his dorm room screaming we see (and have seen multiple times prior to this) the wall and bathroom door opposite his door. Oddly enough, in the next shot from the hallway, Sam, Mikaela and Leo are actually leaving from a door that's farther down the hallway. Sam's actual door is the first one on the right, opposite the bathroom door - there is a bike wheel leaning against the wall beside the bathroom door.
Plot hole: Simmons stands outside the 'The Monastery' at Petra (not to be confused with 'The Al Kazneh' at Petra where Indiana Jones and the Last Crusade was filmed) and looks at the horizon, and he is able to see the Air Force landing with Optimus by the pyramids. It then appears to take them mere minutes to drive over there. This is outright laughable, even accepting that they make the trip in an alien robot car. Petra and Cairo are separated by hundreds of miles of desert, not to mention Israel being between Egypt and Jordan.
Continuity mistake: The Saturn that Mikaela is driving has a moonroof that encompasses most of the roof, over the front and back seats. When the Decepticon Grindor captures them, in the interior shot looking up at Leo as Grindor seizes the Saturn, the car has a solid roof over Leo, which is also seen in the interior shot as they fall.
Factual error: The team go to the Smithsonian Air and Space Museum's Stephen F. Udvar-Hazy Center, which is located adjacent to Dulles Airport in Virginia - surrounded by rolling green hills - to find a Transformer. When Jetfire breaks out of the museum, beyond the broken door is a large, desert airplane graveyard with large mountains in the background. This appears to be the 309th Aerospace Maintenance and Regeneration Group (309 AMARG), a well known aircraft 'boneyard', located at Davis-Monthan AFB, in Arizona.
Visible crew/equipment: When Ron and Sam are discussing college and girls, in the shot facing Mikaela, as she's airbrushing the design on the motorcycle, the reflection of a crewmember (wearing a blue shirt) holding a reflector screen is visible on the chrome surface at the left, and as the camera pans in closer to her its moving shadow is also visible.
Continuity mistake: When the Saturn has been dropped by Grindor, as the car falls with Mikaela, Sam and Leo inside, just before they crash land in the last interior shot, Mikaela's and Sam's headrests have vanished, and a large sticker has also suddenly appeared on Sam's visor in this shot. The headrests reappear when they are upside down.
Continuity mistake: When Lennox is demoted his rank is ripped from his shirt, but when he turns around his rank is back where it was originally.
Continuity mistake: At the Smithsonian Air and Space Museum, when Mikaela, Sam and Simmons follow Wheelie they reach Jetfire's enclosure with the large information plaque attached to the metal front bar, as Wheelie faces them. Next shot, that whole front horizontal bar is gone along with the information plaque, and Wheelie now faces Jetfire. Then when the Cube shard attaches itself to Jetfire the metal horizontal bar reappears, though the large plaque is still gone, and that bar vanishes once again in the shot from under Jetfire.
Continuity mistake: Mikaela is wearing high heels when she reaches the stairs, before entering the library. Then in the library, her high heels have vanished and she is suddenly wearing flat shoes in this scene.
Continuity mistake: When Mikaela, Sam and Leo get into the Saturn there are no headrests on Sam's and Mikaela's seats, but when they kill the Pretender and are driving away, the headrests are suddenly there.
Continuity mistake: When Mikaela phones Sam and says that she's breaking up with him, in the first shot of Sam as he walks down the hallway toward his room there is no curtain in front of the window to the right, but in the second shot as he reaches his room, there are white curtains draped over the windows. Then, when Sam runs into the hallway because of the fire, the curtains are gone again. In fact, the white curtains are actually outside the window - someone had closed the windows over the curtains. The curtains reappear again when he runs back into his room with the extinguisher.
Factual error: In the scene where Galloway parachutes out of a C-17, Major Lennox asks Galloway if he is "familiar with the standard MC-4" parachute as he is helping Galloway don said parachute. The parachute that actually deploys when Galloway pulls the ripcord is not an MC-4, as MC-4 parachutes have rectangular canopies (shown correctly later in the film as the NEST team descends into the desert).
Visible crew/equipment: After Bumblebee has blown up Sam's bathroom and Sam orders him to get in the garage, as Judy shouts, "Holy mother!" the reflections of the moving boom mic and two crewmembers (one wearing blue short sleeves and the other wearing white short sleeves) are visible in the window to the right.
Continuity mistake: At NEST headquarters in Diego Garcia, when Galloway arrives holding up the Presidential order document, in the shot from behind him as he walks through the front gate, the booth is to his right (viewer's right) and the vehicle to his left (viewer's left), but in the shot facing him the booth is to his left (viewer's right) and the vehicle is to his right (viewer's left).
Continuity mistake: During the scene establishing the Decepticons on the Bayos freight ship, vehicles change. The first shot, overhead, shows Long Haul (green dump truck), MixMaster (grey cement truck), Rampage (red bulldozer), and Scrapper (yellow front loader with wheels). The next shot shows Rampage as being yellow, and Scrapper is now some yellow Volvo vehicle with treads and a claw. Also, by the angle of this shot and based on the previous shot, there would not be an angle to see through the background vehicles. In the next shot, when the transformers jump overboard, Rampage is red again, and the Volvo with treads is now the front loader Scrapper again.
Continuity mistake: When Sam is at the Frat party just after he has written the code on the table with cake, he goes and gets a drink. The glass is full, the camera cuts to the girl talking and then cuts back to Sam and the glass is nearly empty, cuts to the girl again and then back to Sam, with a full glass again.
Continuity mistake: In Sam's dorm room, there is a white mini fridge at the foot of his bed, flat against the wall under the Cloverfield poster. However, when Sam rushes after Mikaela just as Alice's 'tongue' grabs hold of his neck, that fridge has moved to in front of the closet door, but it moves back to its original position thereafter.
Visible crew/equipment: After escaping from Megatron, Sam and company go to a deserted junkyard. When Sam is leaning on the hood and Bumblebee drives forward and flashes his lights, a crew man can be seen in the driver's seat. This has been repeatedly corrected, wrongly, by the excuse that a few Transformers have been seen to create holographic drivers or pilots. This is not inaccurate, but cannot be plausibly applied to this case. (1) Bumblebee has never been seen to do this; in fact, no car-form Autobot has been shown to possess this ability, even in situations where it would seem sensible to do so. (2) There is nobody present who is unaware of Bumblebee's true nature, therefore he would have no reason to suddenly project one. (3) In the shots either side of this, no hologram is present. For the corrections to apply, we would have to accept that Bumblebee, for a matter of a few seconds, chose to display an ability that he's never shown to possess at any other time, in a situation where he has no reason to do so. Clearly this is not a supportable argument. This is a visible crew member and a valid mistake.
Continuity mistake: During the forest scene where Optimus Prime is engaged in a battle to the death, Sam is scrambling for safety. In some of the shots both of his hands are uninjured, but in other shots you can see that his left hand is bandaged/splinted. (This is a result of his "real life" injury in a car accident during filming.)
Factual error: In the original Transformers, Tyrese Gibson's character is credited as and wears the rank insignia of a USAF Technical Sergeant. In Revenge of the Fallen, set two years later, Gibson's character now wears the insignia of a USAF Chief Master Sergeant, three ranks higher than his rank in the first movie. The USAF would not jump someone three grades into the top 1% of the enlisted force no matter what his heroics or experience (that does not even happen to Medal of Honor awardees). Clearly the screenwriters recognized this as Captain Lennox is bumped only one grade to Major despite his actions in the first film and Gibson's character, as noted in another mistake, is credited as Master Sergeant Epps, a reasonable promotion. The costume department simply got the insignia wrong.
Continuity mistake: When the Cube sliver burns through the floor and falls onto the kitchen table, in the overhead shot there is a red stool on the side of the table (bottom of screen) with the bowl of cereal, but as the appliances transform that stool is at the wall beside the doorway. It reappears beside the table a few shots later, as the transformed blender jumps on it.
Continuity mistake: When Judy goes upstairs to pack after finding the baby booties, behind Ron there is a chair at the head of the dining room table, in front of the box he just taped. Then, just before Ron says, "Your mother and I are really proud of you," that chair has vanished, only to reappear when Judy shouts that she's crying again.