Factual error: The opening of the film says it takes place in July 2002, but when we first see Will Smith you can see the World Trade Center in the background which had been destroyed ten months before. I know they made the film before the terrorist attack but mentioning the specific date makes it a mistake.

Continuity: At the beginning of the movie, when Serleena first lands on Earth, her ship crashes into the ground and creates a mound of dirt. When Harvey the dog comes over to check it out, the mound is gone.

Continuity: In the opening scene when Sarleena takes the Vic Secret model's appearance the tenticles are just completing her face when the guy grabs her. He had to have seen the tenticles "building" her as he was walking up to her.

Continuity: When Jay and Tee are at the diner eating pie, when Tee starts to eat his pie a woman with a purple shirt and black skirt walks by. When Tee Starts to cry, a few seconds later, there is a shot of Jay and the same lady walks by again.

Continuity: When Agent Jay and Tee are talking in the diner, a young guy passes behind Jay towards Tee, but disappears when the angle changes.

Continuity: When Frank the dog is growling at the agent in the park his teeth are fine but later talking to Zed he is told he can have better dental. He smiles and his teeth are horrible.

Visible crew/equipment: When Jay enters the tent in which the small alien craft had landed we can clearly see the camera man in the golden reflection. This happens twice.

Continuity: In the scene where Jay and Kay are talking in the mail truck, there is clear blue sky over the left shoulder of Jay. The camera turns to Kay for him to speak and when it goes back to Jay the sky over his left shoulder is cloudy.

Continuity: When Jay and Kay make their visit to Jeebs, Jay is talking to Jeebs and you see Jeebs making a statement about how his business is 'banging' and when he see Kay walk in, he points both his hands at him. The camera angle changes and Jeebes is now seen with only one hand pointing at Kay.

Continuity: After Jay and Kay go to see Jeebs about the deneuralizer, Kay leaves and the bad aliens come crashing through the walls. Jay shoots Jeebs head off and, as it's growing back, he says he got shot "right in the pie-hole" (mouth). However he was facing away from Jay when he was shot and it was above the mouth area.

Continuity: In the scene at the lockers in Grand Central Station, Agent Kay takes his watch, an illuminated Hamilton digital, back from the little animals living there. In one shot, Agent Jay puts an analogue watch in the locker as a replacement, but in the next shot it is the same old Hamilton digital owned by Agent Jay. (This is mentioned in the DVD Audio Comentary with Barry Sonnefeld.)

Deliberate "mistake": When MIB agents exit the lift to get into the main hall of the MIB Office, the lift opens halfway up the wall and they need to go down a little platform. But when K and J return during the lockdown and face the trashcan with guns, the lift opens at floor level, so it can be conveniently peppered with bullets.

Continuity: When Agents Jay and Kay are in the elevator avoiding the garbage can robot who is shooting at them, watch their hands - they move from the wall to the roof ledge for support as the camera angle changes.

Deliberate "mistake": When the trashcan opens fire on the lift with Jay & Kay in, the distance and angles mean it would, at most, be able to hit up to the edges of the rear doors. When the inside of the lift is shown, the bullets have somehow managed to reach right to the edges of the lift.

Visible crew/equipment: When agent Kay is in the elevator with the little worm dudes he swings down and starts shooting at the robot. When he swings down you can see the safety harness between his legs.

Continuity: When Agent Kay empties his guns shooting at the trashcan robot in the elevator, he throws down his guns and swings back to the roof of the elevator. When the robot moves into the elevator, the guns are nowhere to be seen.

Continuity: When Jay is in the fight scene with Jarra and his clones, Jay jumps up two clones to get to Big Jarra, but when the camera angle changes, the Jarra clone he jumped on is gone.

Continuity: During the fight scene with Jarra, Jay is dropped into the center of some large plastic tubing, but when the camera cuts to a closer shot, Jay is now seen at the edge of the plastic tubing.