The picture of Galwyn in his human form (before being turned into a mushroom) that Eunice St. Clair shows to Harry Potter Jr. is in reality a caricature of the film's director, John Carl Buechler.
The hero of this film is a boy named Harry Potter and he is surrounded by a fantasy world of witches, wizards and magic - eleven years before J.K. Rowling's Harry Potter novels swept the publishing world.
This is Julia Louis-Dreyfus' film debut.
The green and white hat that Harry Potter Sr. wears at the beginning of the film is from the Real Betis Balompie, a soccer team from Sevilla, Spain.