Other mistake: Jensen (U.S. Army West Point Officer) addresses himself as a Second Lieutenant, but upon closer inspection of his rank (bars on his shoulders), they are Silver. Silver bars indicate a 1st Lieutenant, Gold indicates a 2nd.
Continuity mistake: Before Kay erases the memories of the border patrol cops, he holds the neuralizer with his left hand while adjusting its knobs with his right hand. In the next shot, he's holding the neuralizer with his right hand.
Visible crew/equipment: When J is going to use the neuralyzer on K, on J's lenses you can notice that K has been replaced with a white screen used for lighting.
Continuity mistake: During the written test, Hudson accidentally pierces the page with his pencil. He then reverses the pencil so the eraser is towards the paper. After the cut to Jensen trying to work on his, Hudson's pencil is suddenly corrected with the point towards the paper.
Other mistake: After Mikey is gone, the guard comes down the embankment. As he does, the background "sky" now seems to have a long multi-story building outlined in it.
Continuity mistake: After D is knocked down, K draws his weapon. In one shot of Mikey running, K has his gun aimed directly at Mikey. A moment later, K is shown aiming at Mikey again.
Visible crew/equipment: As K goes to tell Mikey to be quiet, the corner of the sound stage can be seen over his left shoulder.
Revealing mistake: As K walks out from the car, saying "INS, Division Six", look at the road they just drove up. It runs a short distance, and ends at a hill of dirt. Presumably, the pile and the end of the road are at the sound stage wall.
Continuity mistake: When Jay touches the ball that goes flying around, the ball goes past the Immigration Stats board where the time reads 33:01:42 pm. Then when we see the alien surveillance map, the time is 30:21:40 CTN. Then the second shot of the map, the time reads 32:01:42 CTN.
Continuity mistake: In the opening scene, when the van is approaching the road block, you can see the 4 sets of headlights. However, when we see the road block from behind, we see one cop car parked at an angle, in front of another cop car's headlight, which would obstruct the view of the light which we saw before.
Revealing mistake: When James Edwards (later, J) catches the alien in the beginning and has him next to a wall, the alien pulls out a "reverberating carbonizer with mutate capacity" to shoot J. A quick tussle, and the alien drops the gun. When the camera goes to a close up on the gun, watch carefully. You see it quickly fade out of view after it comes to rest, and replaced with a few burning sparkle effects to simulate disintegration.
Continuity mistake: After Laurel is abducted and Jay tries to find her in one of the cabs, Kay brings the LTD around to pick Jay up. The LTD stops beside Jay in a position parallel to the white lines in the road. Jay gets into the LTD and when Kay drives off the LTD has noticeably changed its angle to the white lines even before it begins to move.
Continuity mistake: When K and D are talking to Mikey, they are standing in a clearing with no grass on the ground. When Mikey spots the trooper behind him, he turns and starts running towards the trooper, and he is running down a pathway in the grass. When K shoots Mikey and he is blown apart, there is a shot from the trooper's point of view towards K and D, and the pathway that Mikey just ran down is no longer visible and K is no longer standing in a clearing.
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