Factual error: When Holmes gets rundown by the carriage, he gets taken home and Watson ministers to his head wound. Holmes gets up a short time later and refers to the carriage as a hansom, which is a little two-wheeled cab. The attacker drove a brougham, with four wheels and four-in-hand horses. Even with a slightly bruised head, the master of observation would never make this simple yet telling mistake as he's shown seeing the carriage. The type of carriage is vital to the plot later as it suggests the wealth and status of the murderer and it appears to be used to commit the crimes.
Factual error: The toy horse on Alec's shelf is a 64 Black Foundation Stallion, available from Breyer between 1977-1987. But the film is set over thirty years earlier.
Factual error: In between the scenes when they are leaving Earth and passing through the Jupiter system, you can see stars flying by on the viewer. How could they be flying by stars if they haven't even left the Solar System?
Factual error: When Dave is "true"ing his wheel, he adjusts one spoke with 3 full turns. That wheel would not be rideable after that much adjustment on one spoke.
Factual error: Mike attaches a shotgun shell to a hammer to blow a hole in a door. This would be quite likely to kill him - in a shotgun blast, the explosive force, and hence the buckshot, is channelled along the gun barrel. Without a barrel to channel the force, the blast would send buckshot in all directions. (01:00:40)
Factual error: When Mission Control talks with Challenger 2, the Spacecraft's camera feeds of the Crew are displayed up on two wall-sized TV screens. Between them is the familiar Mercator map of Earth with the ground track of a low-orbiting satellite superimposed. Challenger is nowhere near low orbit: it's out past Mars, in the Asteroid Belt. The middle screen would have a schematic of the ship's interplanetary path.
Factual error: The African American gang the Del Bombers are all wearing Afros. This is 1963 and it would be another 3 years before you would even see these on Black leaders like Eldridge Cleaver and Stokely Carmichael. The only way kinky curly hair was worn back then was very short...later known as a Caeser. Worn any longer would have usually been processed. Some members of the same gang are also wearing open African shirts. These were not available at all until the mid to late '60s and were not worn in the Bronx at all until the early '70s. I think whoever outfitted these guys had the Back To Africa movement confused with the Nation Of Islam which was the only Civil Rights affiliated organization, besides Dr. Martin Luther King's, around at the time and that they wouldn't have belonged to anyway.
Factual error: Buck Rogers is supposed to be a Captain in the Air Force, but he is wearing Navy wings. In fact he is not even wearing Naval Aviator (pilot) wings, he is wearing Naval Flight Officer (navigator) wings.
Factual error: In 1947, when George is 14 years old his father takes him to the clinic for a physical examination. This is about 18 minutes into the movie. The nurse measures his blood pressure using a cuff that is held on with a "Velcro" hook-and-loop fastener. Velcro wasn't marketed until the early 1960's. [A new DVD was released in 2014. The sound track in this scene was edited and we can no longer hear the sound of the Velcro being unwrapped.]
Factual error: There were no gourds in Ancient Judea, of that type. The 'gourd' mentioned in the Bible refers to a colocynth plant, which yields only a small fruit, 5 - 10cm diameter. The gourd in the film is from a pumpkin, and not from a watermelon, as others have suggested. Pumpkins originated in the Americas, and there weren't any in the rest of the world before Columbus.
Suggested correction: This is a movie where Brian falls inside a flying UFO with alien pilots. I seriously doubt that the filmmakers had any intention whatsoever to be historically accurate.
Regardless of the random UFO scene, this is still a factual mistake. It doesn't matter if a film maker sets out to intentionally make a historically accurate film or not. There's nothing to suggest this film was set in an alternate past or that it was a sight gag as if it was a Mel Brook's film.
Factual error: When they visit "Ireland", presumably the Irish Air Corps aerodrome in Dublin at the time of WWII, all of the staff in the bar at the aerodrome are American servicemen, in neutral Ireland.
Factual error: In the opening credits, the camera is making a slow pan across a suburban neighborhood street following a row of houses. In one the driveways is parked a white 1965 Chevy Impala, although the film takes place in early 1963.
Factual error: Marie plays a horn solo on the beach. At times continuous sound is coming out of the horn while she is inhaling through her mouth. Horns only produce sound when the player exhales.
Factual error: Harry goes to the synagogue, to go through a register his grandfather's records. But he is holding the Talmud and not a register, which is entirely and Hebrew, and he's looking at it upside down. (01:05:00 - 01:06:00)
Factual error: The TV remotes of the day wouldn't control more than one TV at a time, yet they all come on and go off at the same rime.