Audio problem: In the scene where Freddy cuts off a doll's head to replace Wondermut's old toy Bob, there is a close-up of the doll head being shaken with Freddy's head visible in the background. You hear Freddy saying, "Look Wondermut. I found Bob," but you can see that Freddie's lips aren't moving.
Continuity mistake: When Gills is trying to find someone to teach the summer Remedial English class, Shoop decides to hide behind the bush in the parking lot to avoid being asked (he's going to Hawaii with Kim). Gills finds Shoop when Wondermutt (the dog) follows Shoop behind the bush. But, if you look closely, you'll notice that there's a shot of Wondermutt following Shoop behind the bush and then two shots later he runs behind the bush again (that's how Gills finds Shoop). Wondermutt runs behind the bush twice.