When the boys go to Uncle Harvey's house and the girls put the lei's on the boys, Jason Priestly's changes from white to yellow and then back to white again as they move through the scene.
After Ned Bleuer rips Roy's shirt, the shirt is alternately on/off Roy's shoulder between shots.
The houses used in the movie were not the actual house Marilyn lived in. There was no upstairs to her actual house. Also, Marilyn had large wooden gates which were locked making it impossible for the boys to get in.
Marilyn Monroe's housekeepers name was Mrs. Murray and not Mrs. MacDonald.