Continuity mistake: After chasing down Sully, the yellow Porsche is totally wrecked on the left side, until Arnie drives it away, and it's fine.
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.
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?
Continuity mistake: After the scene at the petrol station where we see Louis' new car, there's a high shot of him pulling up to a traffic light, with a car on the right of the screen about to pull alongside him. We cut to a shot inside looking out of the left window, so we should see that other car come into view, but it just vanishes.
Factual error: The movie's opening scenes take place in 1951. Frankie sings a line from the Rays' "Silhouettes," a song which was released in 1957.
Factual error: The movie is set in 1882, however there is a scene where he meets Doc Brown with his DeLorean. Back to the Future Part III took place in 1885.
Continuity mistake: Fairly early in the movie, Margo comes to see Nick, who is upstairs in a bedroom. The press is outside clamoring, and Margo locks the deadbolt on the front door. After her talk with Nick, she's in a hurry, rushes downstairs and opens the door without unlocking the deadbolt.