The phone number Mary Lou writes on the confessional booth "For a good time call" was actually screenwriter Ron Oliver's home phone number at the time. No one called.
Almost every character in the film shares a last name with a cult film director (especially horror directors) such as Wes Craven, Stephen King, George A. Romero, Tod Browning, Joe Dante, John Carpenter, John Waters and Frank Henenlotter.
Written and filmed as The Haunting of Hamilton High. The title was changed to Hello Mary Lou: Prom Night II by the Samuel-Goldwyn Company who purchased it and decided to market it as a sequel. The similarities to the original Prom Night (1980), such as the name of the school, and the line "It's not who you go with, it's who takes you home", were entirely coincidental.
When tasked with directing reshoots, first-time director Ron Oliver called Wes Craven for some advice on directing a teen horror film. His advice was, "Give them a scare, give them a hard-on, send them home."
In one of the few positive reviews of the film, The LA Times called it "The Blue Velvet of high school horror movies."