Continuity mistake: As Hermione walks toward the troll, just before she asks, "Is it dead?" the long towel hanging from the rod beside the sinks is visibly straight. When Harry lifts his wand with troll booger/bogey, in the shot of him as he grimaces and groans, the towel on the rod is visible behind him and it's messy. Yet when McGonagall, Snape and Quirrell walk in, the long towel is straight again.
Picture edited by Super Grover
Continuity mistake: After Gerry gets smacked in the face by the 'broken' suspender clasp, we see the silver clasp land under the dresser. Yet, when he's moaning and lifting his leg to get onto the bed, we can actually see the clasp still intact on the front suspender that came loose, which is dangling right behind him (just look between his legs). Of course, in the next shot, that clasp is gone. Since the silver clasp is one of the plot points, this is bizarre to say the least.
Continuity mistake: When John and Catherine are in the hangar at the runway, the Cessna's tail number is N3035C. When the plane is shown in the air, the number is N3973F. When they land, the tail number has changed back to N3035C.
Continuity mistake: In the bedroom scene the girl is holding a clear cup full of beer. The camera goes off her and when it comes back she is holding a blue cup. The camera goes back off her then on her and the cup is clear again. [This mistake does not appear in the unrated version - the blue cup scenes were shot specifically to secure an R rating from the MPAA because the contents are obscured.].
Continuity mistake: When Sam is in his bedroom, after he finds the Cube sliver it falls and dramatically burns a hole through the floor into the kitchen. But Sam's bedroom is over the living room (there is nothing on the ground floor below Sam's elevated bathroom, and in the first movie Jazz hides in this open space), and the kitchen is actually located between the den and dining room, at the other end of the house. If they were to follow the actual floor plan of the house, the Cube sliver would have landed in the area of the piano in the living room, but where would the fun have been in that?
New this month Revealing mistake: During the car chase when the car gets hit by the truck and goes into slow motion you can see the roll cage inside the car.
New this month Factual error: When the returned soldiers are on the train at the end of the film, it's an open plan post-war British Rail Mark I type, which where built from around 1950. Also the blue upholstery on the seats looks to be the corporate blue introduced by British Rail in the 1960s, used by the preserved railway owning the stock, and not what would have featured in Southern Railway carriages of the time. The carriages also have horizontally-sliding windows, which are far more contemporary than wartime trains, which had windows with a much larger vertical opening, held in place by a leather strap.
Plot hole: There's no way that Eddie and Nana left the flooded theater without getting a single drop of water on them. The water flooded up to the ceiling and there's no other way to exit besides the front doors, and Moon's secret exit, which also floods. They do not leave through either way.
Factual error: When Packard and his men arrive on the island, they are seen wearing ALICE gear (All-purpose Lightweight Individual Carrying Equipment). The film takes place in 1973, that type of gear would've just finished testing phases in 1973. The soldiers would be more accurately equipped with M-1956 Load-Carrying Equipment (LCE) or M-1967 Modernized Load-Carrying Equipment (MCLE).