Trap Happy (1946)

Continuity mistake: When Tom picks up a telephone book, you can see he is holding the book with both hands, but when we see a close-up of the "Ajax Mouse Exterminators" in the next shot, his hands are nowhere to be seen.

Continuity mistake: When the mouse exterminator takes a magnet out of his bag to attract Jerry who has eaten a steel nut, you can see there is nothing coming out of the bag, but when the exterminator has captured Jerry, an axe appears out of nowhere.

Continuity mistake: When Tom and the mouse exterminator pry up the entire wall to catch Jerry, the exterminator's feet are positioned sideways, but in the next shot they are facing straight.