1. Sigourney Weaver Never Starred In Ghostbusters - Be Kind Rewind
The references in Jack Black and Mos Def's underrated love letter to film-making come thick and fast thanks to the central conceit that the video store employee and his slacker friend are forced to remake (or swede in the terms of the film) classic movies when Black's character wipes them all. The film offers wonderful nods to the likes of Driving Miss Daisy and Rush Hour 2, but it is the most famous reference point - to Ghostbusters - that creates the alternate universe paradox.
When the films are shared with the patrons of the video store, the popularity draws the attention of the film studios, who send a pair of bailiffs to enforce their copyright claims, one of whom is played by Sigourney Weaver. So basically we have the situation where the Gatekeeper turns up to help sue people over a film she basically starred in in a different universe.
Which other confusing paradoxes are created in movies? Share your own picks below in the comments thread.