Edwin S. Porter: Uncle Josh's Nightmare (1900)

http://www.brevestoriadelcinema.org/storia-del-cinema/02-il-cinema-delle-origini/02-5-nascita-e-sviluppo-della-cinematografia-americana/
Poor Uncle Josh is trying to get to sleep, but being constantly bedeviled by a fellow in red long underwear with horns. A short early trick editing film using a stationary camera much more valuable for its historical, rather than entertainment value.