Continuity mistake: When J and K first get in the car (the Ford POS),the windows keep switching from up to down. Interior shots Will Smith's window is up, exterior shots his window is down. (00:40:30)
Revealing mistake: When J and K get into the car (a POS if memory serves) K makes a comment about J fastening his seatbelt, if you watch in the background out of J's window as they pull away there are a few people walking at an incredible rate showing that they filmed the scene at a normal speed then sped it up when put into the final cut. (00:40:40)
Continuity mistake: Just before the diner scene, where the two aliens are discussing the galaxy, we see the outside of the Russian restaurant. The neon sign says "haroshaya" meaning "good" all the way across the window, in the next shot inside the restaurant, the "ha", which looks like the English letters "xo", is gone and the sign is centered. (00:41:00)
Continuity mistake: When the two men with the cat are eating at the diner, the table behind the old man is either empty or has an old woman sitting by it, depending on the angle. (00:41:30)
Continuity mistake: In the restaurant scene, the jewel case containing the diamonds is to Mr. Rosenberg's right, but when the Arquillian asks what it is, the jewel case is to Mr. Rosenberg's left. (00:41:55)
Other mistake: When the two men are in the diner before they get killed by Edgar the bug, the subtitle reads, "Sure. I ordered you some Pirogi". The correct spelling is Pierogi. (00:42:00)
Other mistake: There is a mistake in the French subtitle translation. In the diner when the cook asks Edgar the Bug, "where's Ivan?" Edgar responds, "[I] gave him a break". The translator writing the subtitles must have thought he was saying "GIVE him a break" because the subtitle reads, "laisse-le tranquille" which means, "leave him alone". (00:42:10)
Continuity mistake: When the cat in on the table in the diner, the word "ORION" on the cat's collar is in normal capitalized block lettering. But when the cat is on the table in the morgue, the word "ORION" is in calligraphy. Also, the colour of the cat's collar seems to change between these two points. (00:42:40 - 01:08:15)
Continuity mistake: When the farmer kills the two men at the diner he exits the place and encounters a passer-by. When the angle changes the man has vanished. (00:43:05)
Revealing mistake: When K and J buy the "hotsheets" (newspapers) to look for information, the clerk who K gives the money to briefly looks at the camera. (00:44:00)
Continuity mistake: When J is trapped by a tentacle of the alien woman in the car, the first seconds of him being dragged up and down he casts no shadow on the ground. Later on when the tentacle is extended he does cast a small shadow. (00:44:10)
Continuity mistake: When J holds the baby squid, his fingers protrude more or less depending on the angle. (00:44:40)
Continuity mistake: When Arquillian's stretcher is about to pass through the doors, the cat is raised and nervous, when the angle changes he is resting relaxed. (00:50:00)
Continuity mistake: When Arquillian's body is brought to the morgue, the strap around his legs disappears in the first shot. (00:50:00)
Revealing mistake: When Arquillian is laying flat dead in the morgue, his pulse on his throat is very visible. (00:50:35)
Continuity mistake: After Dr Weaver unveils Arquillian's body, the way the blanket is folded changes between shots. (00:51:55)
Continuity mistake: At the morgue, K walks towards the Arquillian's head while Weaver and J walk to see the Jeweler. When the angle changes, a frame later, K is meters away, close to the racks. (00:52:00)
Revealing mistake: When the jeweler's ear pops-open, the angle changes and it gets replaced for a prop that looks nothing like the real ear. (00:54:35)
Factual error: When Tommy Lee Jones is looking at his wife on the computer, he had typed in Truro (in Cape Cod, Mass.), but when he zoomed in, it was on the lower cape; Truro is located on the upper cape near the tip. (00:58:40)
Revealing mistake: There is a scene where Agent J is standing on a car and shoots the "Noisy Cricket" at the fleeing Edgar. The camera shot is from inside the car and just before Agent J crashes through the windshield, you see a precut area in the glass. (01:01:25)
Answer: David Cross plays Newton in both movies. In the first he is attacked by the Bug but survives and something went wrong with his neuralyzing as in the sequel he knows small things about the men in black like how they appear and he recognises the neuralyzer from his previous encounter with it, which isn't a coincidence. It appears J's neuralyzing of Newton did work and we don't see him in the 3rd movie (probably because he is in jail for the murder of his mother).
lionhead