Hmm. I do suppose that this would probably support the 'fiction' theory - common points between our universe would come from the 'real' world, where all the authors and producers grew up.

If there are infinite universes, and ours just happened to be close, you get the problem of how two people from the exact same universe would both come here, then. Though that's assuming the selection is random. If those running the island are able to select specific universes, no reason they wouldn't be able to do so twice.