Movie Goof (revealing mistake): When Rocky looks in the carnival mirror it alters his deformed face to appear almost normal. They send for his mother (Cher) to look at him. The same mirror that altered Rocky's face to appear normal should have deformed his mother's face. But when you see them looking in the mirror, Cher's face is looking perfect. Also, Rocky's nose casts a shadow in the mirror; on his actual face, the bridge of his nose casts no shadow.
Movie Goof (errors made by characters, possibly deliberate errors by the filmmakers): When Laura Dern is leaving the camp (right before her parents arrive) you can clearly hear one of the children that she hugs refer to her as Laura instead of Diana, her character name.
Movie Goof (anachronisms): When Cher opens her beer can in the camping scene near the beginning of the movie, the can has a stay tab. These were not used on cans until the 80s. Cans prior to then used pull tabs.
Movie Goof (continuity error): At the beginning of the film, Rocky has two Steve Garvey cards. Red gives him another one, making him have three Steve Garvey cards. A little bit later, Rocky gives one of his Steve Garvey cards to Ben, leaving him again with two Steve Garvey cards. When Rocky and Rusty have their fight about Rusty going out all the time, she rips one, which should only leave him with one whole card left. But when he goes and finds the other cards that match the ripped one, he has a total of three. Since he gave one away to Ben and his mother ripped another one, he should only have a total of two Steve Garvey cards (the ripped and the whole).
Movie Goof (factual errors): When Rocky nervously rides up next to Diana on his slightly out of control horse he chuckles and makes the comment, "On your right". He is actually on her left... his right.
Movie Goof (factual errors): SPOILER: In reality, Rocky's body was donated to the University of California, he was not buried in a cemetery as being shown at the end of the movie.