When Maurice says, "It's magic!" and creates "sparkles" with his hand, he's really only throwing glitter (You can see some of it sticking to Fred Savage's shirt before the scene ends).
During his first trip to the monster world, when he's asking to make a special trip to (Ronnie Coleman's house), Brian is wearing the clothes he's wearing on his second trip, red t-shirt with a dark button up shirt over it, instead of the shorts and t-shirt he had gone in with.
When maurice has some creature pop out of his head, you can see that is is a puppet from the side of his head
Contributed by: Anonymous
When Brian finds the TV on with 'The Fly' playing, it is on a Sharp brand television, however, the remote control that drops to the floor is a Sony.
When Eric's friend Todd sleeps over and tells him a ghost story, he calls Ben Savage by his real name. ''I'm deadly serious, Ben.''