A fan film is a film or video inspired by a film, television program, comic book or a similar source, created by fans rather than by the source's copyright holders or creators. Fan filmmakers have traditionally been amateurs, but some of the more notable films have actually been produced by professional filmmakers as film school class projects or as demonstration reels. Fan films vary tremendously in length, from short faux-teaser trailers for non-existent motion pictures to rarer full-length motion pictures.