Best animated movie mistakes of 1955
Continuity mistake: When Uncle Pecos breaks his guitar string whilst rehearsing in Jerry's home, he goes up to Tom and pulls off one of his whiskers. The whisker Pecos pulls off is the one on the top left of Tom's face, but when Tom goes to check his face in the mirror a few shots later, the whisker Pecos pulled off is still intact, and the whisker in the bottom right has been pulled.
Continuity mistake: When the Coyote attempts to capture the Road Runner for the first time, he is standing on a bare patch of pavement surrounded by the puddle of glue he is spreading. In the next shot, the Coyote is now standing on glue with no bare patch, and when he realises he is about to be hit by the truck, he is standing on bare pavement in middle of the glue puddle once again.