Continuity mistake: In the last scene at the diner, the various camera angles show the background characters. The view to Will Smith's right shows 5-6 empty seats down to a man at the end of the counter. When Smith and Jones leave, the camera pans left down the same seats and there is Griff sitting 2 stools away from Will's spot. He wasn't there 10 seconds earlier and has partially eaten food in front of him, indicating he was there for a while. And you think Will would have noticed him there after all they recently went through.
Continuity mistake: When K and J drive to the bowling alley, the same junction with a shiny blue car and a man wearing an orange shirt is seen three times through J's window.
Continuity mistake: At the bowling alley, after K polishes the alien's head, the way his hair is messed up changes between shots.
Continuity mistake: When K questions J at the headquarters, K grabs his tie. From the immediate angle his hand is lowered.
Visible crew/equipment: After J arrives in 1969 and stands on the sidewalk at the Empire State Building, look at the doors behind him. As they close and open, the lighting rigs are reflected.
Continuity mistake: As J flies backwards after the fish creature sneezes, he breaks through the plate glass window, and has the bottles in his hands. After the cut, he's just breaking the glass, and the bottles are missing from his hands.
Other mistake: When K wipes little James' memory at Cape Canaveral, he uses a small neuralyzer, but we've seen at the beginning that in 1969 the MiB only have the big tubes, and K doesn't have J's future neuralyzer anymore; he gave it back already after their mono-wheels chase.
Suggested correction: What K has is probably their first and only portable neuralyzer, maybe even a prototype. The big one is their main neuralyzer. You may notice there are no dials on this one, so he has no ability to wipe a specific amount of memory.
Continuity mistake: When they pull up to Cosmic Lanes, they park right next to a telephone pole, but when the shot watches K get out of the car, there is no telephone pole; instead, there is a freshly planted tree.
Continuity mistake: When J is shown the time-jump gear, the box is to the left of a pair of earphones and just an inch away from the log journal in front. When the shot changes the earphones are between both.
Continuity mistake: When Obadiah stands on the Chrysler building terrace his hair is either loose or tucked behind his ear.
Visible crew/equipment: As K opens the door to the Cosmic Bowl bowling alley, the camera crew and equipment is reflected in it.
