Audio problem: When Will Smith is looking at the two space ships at the MIB headquarters, if you look in the background Zed and K are there typing on the computer. But if you look closer you can tell that they're not even touching the keyboard and the sounds are just added into the movie. (01:16:00)
Continuity mistake: When Joe is on the yacht talking to his father, Joe is mixing up martinis, pours them, and adds an onion to one, and then an olive to the other. The camera cuts away to his father and then cuts back and now the second martini has no olive, so Joe adds an olive again. (01:30:11)
Visible crew/equipment: In the scene where the knights are attacked by the killer rabbit outside the cave, you can see the boom mic at the top of the frame.
Continuity mistake: When the kid rescues Bud from his former owner, Buds paws become all muddy when the faucet breaks. In the next scene they are running down the road and Bud's paws are clean.
Revealing mistake: When Troy says "I'll sing with her," Ms. Darbus turns around "in response" to his voice before he even says anything.
Other mistake: When Brian takes a picture of his friend Doug on the boat, the picture shows Doug in a different position than that of when the picture was taken. (01:21:30)
Continuity mistake: At the beginning of the movie when Romy reunites with Heather Moony, Heather tells Romy that she invented the cigarette which she is smoking and takes a puff to show how fast it burns down, and the cigarette burns to the butt. But in the next scene her cigarette is still to its half-way point. (00:07:25)
Continuity mistake: Watch the first kiss scene between Reeves and Theron. Keanu's shirt drops to the floor, yet you can clearly see it on his shoulder in every other shot. The camera switches angles multiple times, so this is easy to spot.
Revealing mistake: When Hallie trashes Annie's cabin and the huge water balloon is about to fall on Annie's head, the camera is at a downward view and Annie clearly steps into the trail of the balloon instead of jumping away. (00:18:05)
Continuity mistake: Sheriff Buford T. Justice gets out of his car and leaves the door open. A few moments later, we see a different shot of the car with the door closed. Then a truck drives by and tears the car door off which is open again.
Continuity mistake: In one of the opening scenes when Bob comes in from walking the dog in the rain, he dries the dog off with a towel and puts the towel on top of the coat tree. He tries to feed the dog and when it cuts back to the dog the towel is on the floor, then his wife comes in and the towel is back on the coat tree.
Continuity mistake: When Larry and Nick Daley first enter the British Museum, Nick takes his beanie off twice, in consecutive shots.
Plot hole: When Andy turns into a werewolf, he kills both Amy and Detective Benbou. Later in the morgue, Amy tells him because of this that she is forced to become his "rotting sidekick." If this is completely true, then Detective Benbou should also be following Andy around but he isn't seen after Andy manages to escape from the morgue.
Factual error: The movie is set around 1995. But the SWAT team in the movie is wearing gear from the 2000s. (MICH-2000 helmet, modular tactical vest, M4 variant with picatinny rails and scope). Plus, in a scene when the guys are shopping for a taser (gun shop scene), some of the rifles on display are from 2000s era. AR-15 variants with variant stock, foregrip and picatinny rail. Those style of weapon system were unheard of in early 90s. Even Special Forces just adopted it by the late 90s.