Continuity mistake: If you look carefully at the monster (Frankenstein) you will see that his face is different in the ending scenes. The reason is, during the movie you see the monster take the woman doctor and throw her out the laboratory window. You then see the monster kind of stumble, which he really did and broke his ankle. So in the final scenes they replaced Lon Chaney Jr. as wolfman with a stuntman, and Lon Chaney Jr. finished the movie as the monster.
Continuity mistake: When the ants have Donald's hat, they throw it over the edge of the cliff. When we see Donald in the river in the next shot, there is no sign of the hat.
Revealing mistake: When Mr. Peabody is fishing, it is obvious that he is in a boat on the floor of a studio. Rear-screen projection is used to show the ocean behind him, but while he is standing in the boat and trying to reel in his catch, the boat is absolutely motionless.
Continuity mistake: When the big dog points his gun towards the hole in the log, the length of the log changes between shots.
Continuity mistake: When Bugs is about to tee off at the first hole at the golf course, the objects behind him change position between shots.
Continuity mistake: When Sam says to Bugs, "This town ain't big enough for the two of us", Bugs is holding a carrot in his right hand. When Bugs runs out of the saloon in the next shot, the carrot he was holding has disappeared.
Revealing mistake: When Tom is punctured in the rear by the fork that Nibbles is holding, his tail is missing.