Continuity mistake: When Droopy is standing the door, he tells the convict he's going to call the cops. At this point you can see there is nothing next to Droopy on the frame, but in the very next shot a hinge has appeared.
Continuity mistake: When Jerry slams the door on the dollhouse after Tom attempted to catch him after his dress slips off, the blind in the top window is pulled right up but in the next shot it's now pulled down halfway.
Continuity mistake: When Bugs is viewing footage of the previous encounter between Cecil Turtle and himself at the start of the cartoon, you can see that viewed from behind, the projector only has one reel. When we see Bugs eating his carrot in the next shot, there are now two reels.