David Mucci, who played troublemaker Lou, had a serious medical condition. He was forced to be immobilized underneath the stage for the scene in which Lou is decapitated. He was terrified that something would happen while he was trapped there so director Paul Lynch held his hand for the duration of the scene to assure him everything would be all right.
In one of several scenes removed from the theatrical version of the movie, Principal Hammond takes his wife to visit Dr. Fairchild after a visit to Robin's resting place at the cemetery. As Vivian is seated in the office and the men talk privately in the hallway, it is revealed that Robin and Alex are twins.
According to director Paul Lynch in the documentary "Going to Pieces: The Rise and Fall of the Slasher Film", he was having difficulty securing financing until Jamie Lee Curtis signed on. Once the film was shot, Paramount expressed interest in distributing the movie. However, they only wanted to open it in 300 theaters whereas Avco Embassy Pictures offered to release it in 1200 theaters. Avco Embassy released Prom Night as a result. That same year, Paramount released another independent slasher film, Friday the 13th (1980).
As gym teacher Henri-Anne Benton is giving decorating instructions to Biology teacher Monty Weller in the gym and Kim runs in, she apologizes for being late and Mr. Weller calls her "The literary Ms. Hammond". This is related to one of several scenes deleted from the theatrical version (but returned to the network TV version) of the movie when the girls are dissecting frogs and are caught sneaking Jude's note about her last-minute prom date, Slick. Mr. Weller wrongfully accuses Kim of possessing the note and forces her to read it aloud to the class.
When Ms. Benson says to Mr. Weller at the prom "I believe this is OUR dance, Monty", he was in the company of Adele Cooper, the substitute secretary for Principal Hammond. She is a character whose scenes were removed from the theatrical version (but returned to the TV version) of the movie.
When the raspy voiced caller in the room dials the residences of Jude, Kelly, Nick and Wendy respectively, the area code on the rotary phone begins with 614. Although the movie was shot in Toronto, Canada this area code is for Central Ohio.
Hamilton High custodian Mr. Sykes, albeit drunk on the evening of the prom, knew that a killer was loose because he was secluded in the same storage room that Wendy ran into when she was being pursued. You can see the camera pan left to his silhouette shortly after she enters the space to hide.