10 Great Horror Movies That Started Out As Short Films

10. When A Stranger Calls

One of the best takes on "the babysitter and the man upstairs" urban legend, 1979's When a Stranger Calls stars Carol Kane as Jill Johnston, a young babysitter who becomes terrorised by a threatening phone caller over the course of an evening. She plucks up the courage to phone the police, who then trace the source of the calls to the house she's babysitting from.

When a Stranger Calls didn't get the best reviews at the time, but it's gone on to become hugely influential, inspiring among other things the opening to Wes Craven's Scream. 

The film was directed by Fred Dalton, who took the idea from a short he'd made two years earlier called The Sitter. The 21-minute film is essentially the first segment of the full feature, with the remainder of the runtime playing out as a response to those events - even following the killer who stalked Jill following his escape from a psychiatric facility.

Dalton and his producer Steve Feke initially tried to get The Sitter nominated for an Oscar, but when that failed, it lay dormant for several years. It was only after the success of When a Stranger Calls that there was renewed interest in the short, which resulted in The Sitter finally seeing the light of day as a DVD extra in 2018.