Deliberate mistake: At the beginning of the movie Mr. Coates tells his wife that he will be gone "all of three months, maybe four." The first time we see Bud and Elizabeth Searcy she tells Travis that her dog is pregnant and that Old Yeller is the father. We then see her dog that does not look very pregnant. The next time we see Elizabeth she presents Travis with one of the pups. The problem is that the pup that was supposedly just born is about 4 months old.
Continuity mistake: During the slow-motion sequence, Speedy slams the mallet on the cat's paw and leaves the mallet on the ground when he rescues the mouse. When he puts a stick of dynamite on the cat's tongue, the mallet has gone.
Continuity mistake: When Speedy Gonzales makes Sylvester jump, you can see that Sylvester's chest is shaven, but when he is chasing Speedy in the next shot, his chest is now its usual white.
Continuity mistake: When we first see the "No Wolves Allowed" sign at the House of Bricks, "No Wolves" is on top and "Allowed" is at the bottom. When The Big Bad Wolf is looking at the sign, the words "No Wolves Allowed" are now on top of each other.
Character mistake: When Bugs is reading the book, he says "Octopuses", but when we see a close-up of the book, it reads "Octopus."
Continuity mistake: When Quackie is at the cafe with Mary, their dog is sitting on the chair between them at the table. But when Inspector Faraway appears, the dog has gone.
Continuity mistake: When the Tasmanian Devil passes by the hamburger stall, you can see there is nothing next to the radio on the counter, but when we see a close-up of the radio in the next shot, there is now a mustard pot and a bottle next to it.
Continuity mistake: When Sylvester is unable to sleep at night, the camera pans in on his eyes and you can see that he has his head on the pillow when this happens, but in the next shot he is lying flat out on the bed.
Continuity mistake: When Yosemite Sam says "I dares" to Bugs, you can see there is nothing behind Bugs, but in the next shot he is standing in front of a mountain.
Continuity mistake: When Daffy arrives at the theatre, there is a billboard behind him saying "Bijou Presents on Stage Tonight." But he points to the marquee in the next shot, the words have disappeared.
Continuity mistake: When Tom is placing a chicken under Spike's arm, Jerry takes a photo and you can see a trail of fake paw marks. When Jerry emerges from the dark room with copies of the photo, he takes one copy from the pile and has a look at it, but the picture shows no paw marks at all.
Continuity mistake: When Ralph is walking up the steps to his apartment, he has a present in his right hand. The present disappears when he goes through the doors, but re-appears when he enters the kitchen.