The parallel universe: How to trace the history of the parallel universe story? Maybe the first literary example is Lewis Carroll�s 1865 novel Alice's Adventures in Wonderland, which finds Alice in a strange fantasy land populated by characters resembling those that the real Alice knew. (Of course, it could be argued that this is a matter of interpretation, since it's not obvious from an isolated reading of the book). A similar device is used in L.Frank Baum�s 1900 story The Wonderful Wizard of Oz.

Perhaps the best-known example in cinema is the 1946 classic It's a Wonderful Life, which tells the uplifting story of a humble, suicidal man (the wonderful James Stewart) who is shown how the world would have been different if he'd never been born.

Many science fiction TV shows have utilised the idea: The 1970 Doctor Who story Inferno saw the Doctor visiting a parallel world where Totalitarianism was rampant. The TV series Sliders used the parallel universe theme. Star Trek has a whole sub-series of parallel universe stories, beginning with the 1967 episode Mirror Mirror and revived and mined for all it was worth by the 90s variant Star Trek � Deep Space 9.