Continuity mistake: Glen Holland owns a Chevy Corvair throughout the film. The car at the beginning of the film is a 1961 model 500 (the base model with bench seats), but at the end of the film it is a 1964 Monza (the top of the line model, with bucket seats).
Continuity mistake: When you first see the Swan boat going down the river with Nutcracker pushing it along with the pole, he is rocking back and forth and you see that he is behind the large swan wings. But in the next shot, he is in front of the wings as he pushes.