Continuity mistake: When Bugs thinks he has escaped from Sam, he finds himself standing in the arena. At this point, you can see there is nothing beside Bugs, but when we see a full view of the arena in the next shot, look at Bugs and you can he has a shadow next to him.
Continuity mistake: When Yosemite Sam is on the stilts whilst walking through the pit of lions, he clobbers a lion with a club. But when Bugs gives the lions tools to cut the stilts down, we see Sam trying to get back to the other side and the club is nowhere to be seen.
Continuity mistake: When Yosemite Sam picks up a club to chase Bugs Bunny, you can see Sam is holding the club with his left hand. But when we see Sam pursuing Bugs in the next shot, he is holding the club with his right hand.
Continuity mistake: When Emperor Nero tells Yosemite Sam to get him a victim, you can see that Sam is holding a sword in his hand. In the next shot, the sword has gone and Sam is now holding a bugle, and when he is marching along with the legion, he is holding the sword again.
Continuity mistake: When Sam closes the door after escaping the lions, you can see there is nothing under his feet, but in the next shot a doormat has suddenly appeared.