Billy is a fictional character from the Black Christmas film series. He first appeared in Black Christmas (1974), as a deranged murderer who taunts and kills a group of college students during the Christmas season. Created by Bob Clark and A. Roy Moore, the character was partly inspired by the urban legend "The Babysitter and the Man Upstairs", as well as a series of real murders in Montreal during the holiday season.
Several members of the cast and crew would portray and voice the character in the original film, such as Nick Mancuso, who performed the voices for the phone calls, while cameraman Albert J. Dunk performed Billy's POV shots and director Clark himself portrays both the villain's shadow and the phone voices. Neither the character nor his portrayer(s) would be listed in the end credits. In the subsequent years following the original film's release, fans and several media outlets have often cited the character's name as Billy, and director Clark has himself referred to the character by that name in later interviews.
Unlike later slasher film antagonists, the character's true identity and motivations were intentionally omitted from the 1974 version of the film, which the filmmakers felt made him more frightening. Several critics and art historians have noted that by leaving the character enigmatic, it allowed the audience to place their own fears onto the character, forming their own ideas about him and his motivations. While largely overshadowed by more popular horror or slasher film villains, Billy has subsequently been identified by some critics and film historians as establishing many of the tropes that later became a staple of the slasher film genre, predating John Carpenter's Halloween (1978). He has been described as one of the greatest horror villains of all time, and has been referenced in several other entertainment media.
"Billy" made his first appearance in the original 1974 film Black Christmas as a mentally disturbed man known as "The Moaner", who regularly calls a local sorority house, leaving disturbing and obscene messages. During one such phone call, Barb (Margot Kidder), one of the sorority sisters, provokes him; he responds by threatening to kill them. The caller then goes on a killing spree, murdering most of the sorority house's inhabitants, including Barb. Jess (Olivia Hussey), the lone survivor, is attacked by Billy but manages to fight him off, and after discovering the corpses of Billy's victims in Barb's room, accidentally bludgeons her boyfriend Peter (Keir Dullea) to death, thinking he is the killer. The film ends with Billy, still alive, talking to the corpses in the attic, before making a final phone call to the house.
Billy later appeared in the 1976 novelization of the film written by Campbell Armstrong under the pseudonyms Lee Hays and the 1983 republished edition as Thomas Altman. Both editions gave the character's name as Billy.
In the 2006 remake, his full name is William "Billy" Edward Lenz (Cainan Wiebe), and his backstory is prominently featured. Billy was born with severe jaundice due to liver disease, and although his father loves him, he is physically and emotionally abused as a child by his mother, Constance (Karin Konoval). After murdering Billy's father along with her lover, Constance rapes Billy after she is unable to conceive a child with her lover, giving birth to Billy's sister/daughter Agnes (Christina Crivici). Billy later goes insane and murders his mother and her lover, disfiguring Agnes before being caught and sent to an insane asylum. Years later, an adult Billy (Robert Mann) escapes and goes on a rampage with Agnes (Dean Friss) at their old family home, which has been converted into a sorority house. After murdering most of the inhabitants, both Agnes and Billy are killed by Kelli Presley (Katie Cassidy), the sole survivor.