Continuity: Right after Zed kicks Serleena in the face a few times, you see Serleena tripping him with the vines from her fingers and he lands on his side. The camera angle changes and he is now seen laying flat on his back.

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.

Continuity: When Kay shoots Jeebs' head off, him and Jay are shoulder to shoulder looking down at Kay. Jeebs' head acts like a popped balloon full of green goo, but none of it gets on Jay or his suit.

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: When Kay and Jay are watching the movie about the light, Kay starts to remember the real story and cries. The shot later, his is cheek is dry.

Continuity: In the scene where agent Jay is looking at MIB HQ and sees the dead alien with tentacles, he sees something (Frank). He tells the computer to zoom in and when it does the tentacle on the right hand side half way up the screen changes shape and position.

Revealing: When Jay is at the post office looking for Kay, he's talking to him in the parking lot and Kay is sitting in a mailman's cart. Jay says something to Kay, and Kay punches him, but you can see that he didn't touch him, especially since Jay reacts to the hit a split second before it happens.

Continuity: When J and Kevin get flushed they end up in 2 cans in times square. In the long shots the cans are the same height, but in close ups, Kevin's is slightly shorter than J's.

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.

Factual error: When Jay and Tee are in the diner at the start of the film, it's 9pm (we know this because Tee started at noon and Jay set the neuralyzer to nine hours), and outside it's completely dark. In New York City at 9pm in July, the sky is not completely dark - the sun would just be setting.

Continuity: It appears Will Smith suffered a touch of acne during filming. In the scene where they are driving to the young woman (witness), Will has a noticeably large spot on his cheek. In the next scene it 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.

Factual error: When Jay and Frank go to Truro, MA, to get Kevin, as they drive in, the background shows the Post Office in front of a lighthouse. However, 1) There is no lighthouse in Truro, and 2) the closest lighthouse is in North Truro, and this lighthouse (the Highland Lighthouse if you're wondering) doesn't even remotely resemble the lighthouse behind the post office. This means that either the shot was filmed in a different place than they say it was, or the background was digitally animated.

Continuity: Throughout the whole movie when someone is driving they keep driving to different locations but if you look out the window it's just the same green background all the time.

Continuity: In the scene where Serleena confronts Zed in his office, look closely at her hands. Immediately after releasing Zed from her tentacles, her left hand now holds a box of Burger King fries, which disappear from shot to shot. This is most evident when she picks up the cellular phone, placing both empty hands on the desk first.

Factual error: When Agent Kay looks up, after he is "deneuralyzed" he sees Orion in the sky. They're in NYC...you can't see the Evening Star, even in the middle of the night. There is no way that Kay could see a perfectly clear, and detailed constellation, complete with stars that can't even be seen in rural areas.

Factual error: In the scene where the half-destroyed subway car arrives in the station, when it stops, you hear a small chime-like noise. In New York City, however, this noise is only made when a subway car's doors shut and it leaves the station.

Other: When Agent J. is riding the Giant Worm in the subway, you see him getting hit by a metal bar on the top of the tunnel smack right in the head at amazing speed, twice! Yes, twice that happened. And later, when he is sitting on the bench with his partner, you see his head is looks complety untouched, no cuts, blood, scars, absolutely nothing. Certainly he would at least have a little mark, but nope, nothing but a little sweat. Does Agent J. have a hard head or what?

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.

Other: When Jay opens the post office sorting machine and we see the multi-armed alien, there is a stereo playing rock music quite loudly. There's also a hole on the other side of the machine (to fire the letters out of) - shouldn't we have been able to hear the music through that hole before Jay opened the machine?