Factual error: Tom Cruise says of the song 'Sitting on the Dock of the Bay' "my folks loved it". However, his father died in 1965, his mother died "shortly after him", and the song wasn't written until 1967.
Factual error: There is no possible method of "fusing" the genetic material of a common housefly (Musca domestica) and a human. The housefly has twelve chromosomes, humans forty six. There is no way to combine the two in order to produce a viable organism. Thirty four of the human chromosomes would have no matching chromosome to "fuse" with, meaning the physical characteristics coded by those genes would not form. The Brundlefly would be missing three quarters of his human body.
Suggested correction: There's no possible way of teleporting physical objects either, but it happens in this movie. This is science fiction. These kinds of "factual errors" are not valid.
The film presents no scientific explanation for "teleportation" but does for "genetic merging." Teleportation is possible in this film's universe, but "genetic merging" is impossible in any universe.
Factual error: During most of the basketball games, you can see an American flag in the background. This is not the problem, the problem is that it is hung wrong, the stars should always be on the top LEFT not RIGHT.
Factual error: While using the phone in his cell, Dr. Lecktor asks an operator to dial a Maryland area code, but is then connected to the University of Chicago. (00:30:10)
Factual error: Teddy wears army boots that did not exist in 1959.
Factual error: Right before Frank humiliates Dorothy for the first time, he blows out one of the gaslights in her apartment. That is never done in real life, for the same reason you would not blow out the pilot in your stove.
Factual error: When Nancy goes in a car in London to score drugs there is a political poster stating 'Labour Isn't Working'. This poster was used by the Conservative party in the 1979 general election - Nancy was killed 9 months prior to this election.
Factual error: Calendar date at the very beginning of the film (in the police station), shows the dates of Saturday 20th/Sunday 21st July 1983. However the 20th and 21st July 1983 fell on Wednesday and Thursday.
Factual error: Bunny bites an aluminum beer can in half. Beer cans weren't aluminum until the mid 70s. He would have hurt his mouth on that one.
Factual error: Cruise is breaking and if you watch the eight ball after the break it's following the 5 into a pocket at the end of the table closest to Tom. Now the 8 ball didn't necessarily go in because they focus on the one ball, but in the next frame shot, there's no way it could be at the opposite end of the table like they show. (00:29:20)
Factual error: The movie they're watching in the theater, "The Fly", is shown backwards. The first scene they see should have happened after the last scene they see.
Factual error: During the karate tournament towards the end of the movie if you'll notice the American flags in the background you'll see that they are displayed improperly. Whether flags are being displayed horizontally or vertically, the stars should always be on the left side of the flag.
Factual error: The clan people look nothing like Neanderthals, they look like Cro-Magnon with a little dirt on.
Factual error: When Fievel is being dressed by the pigeon there are two American flags in the background. The flags have too many stars for the mid 1880s, when the movie is set.
Factual error: The film strongly implies that John Dudley, the Duke of Northumberland, keeps his head (literally) by converting to Catholicism. In fact, he was executed well before Lady Jane Grey was.
Factual error: Towards the last scene, Howell and Hauer share the same shotgun (Ryder to take pop shots at Jim in the jeep, Jim to ultimately fire three shots to kill Ryder). The shotgun used can hold at most seven or eight shells, not the 12 or more that are fired between Ryder and Jim starting from when Ryder escaped the bus.
Factual error: In the scene outside the pub, a Ford Sierra is seen driving past. These were not introduced into the UK until Autumn 1982. The film is supposed to be set in 1981.
Factual error: Throughout the film, they play one of Strauss' Four Last Songs, which is credited as being "September." The song actually played is "Beim Schlafengehn."
Factual error: Oswald says that "Vermeer only painted twenty-six paintings and three of those are dubious." There are in fact thirty-five known to be extant (one recently stolen) of which only one is regarded as dubious. In addition, there have been descriptions of six (or possibly eight) others that seem to be missing. (00:35:10)
Factual error: Why is there gas in the motorbike which is exhibited in the cinema?