The mouse leaves Porky a note saying he doesn't like Swiss cheese, but later on, he grabs a load of Swiss from the round mousetrap.
In close-ups the buttons on the robot cat are solid cylinders, but on all other times they are like old typewriter keys - flat discs with a thin shaft.
There is no door latch strike plate shown in the door frame when Elmer Fudd opens the door in the house in a few scenes.