Continuity mistake: In a full length view of the two forts, Sam's fort has a flag reading "They" and Bugs' fort has a flag with "We" on it. When we see Sam tunnelling underground, the words on the flags are missing.
Continuity mistake: When Bugs is square dancing with the hillbilly brothers in the hall, you can see that the hall has a decoration on the wall, but in the next shot the decoration has disappeared.
Continuity mistake: In the scene where Sylvester tells the bulldog to be quiet when they are in their cages, you can see there is nothing behind them, but when we see the train about to go up a hill, we cut back to Sylvester and crates have suddenly appeared.
Audio problem: When Daffy says "So long, Rembrandt!" whilst pretending to ride on a bicycle, his beak doesn't move.
Continuity mistake: When Porky inspects Prissy for eggs, you can see that the nest to her has nothing on the wall, but when Porky threatens Prissy to lay an egg, a sign with "Daphne" on it has appeared.