Money, Dear Boy: Both leads were only in the film to fulfill contractual obligations, and both would go on to win Oscars.
Sleeper Hit: Arguably the original example. The film was made on a low budget by a small studio and a director that had yet to make a name for himself. Columbia had little faith in the film, and spent almost nothing on advertising, while both of it's stars wanted to distance themselves from the project. The film was originally released to average box office, but positive word-of-mouth eventually spread, and the film amassed a huge cult following, especially in rural areas. It later went on to sweep the Oscars that year, unheard of at the time for a smaller movie.
The film is rumored to have been a primary inspiration for Bugs Bunny, thanks to a scene where Peter talks quickly while chewing on a carrot, as well as another scene where he pretends to be a gangster and invents a person named Bugs.