In 1956, Princeton student Hugh Everett III, writing in his doctoral thesis, first explained the Many Worlds Interpretation (MWI) of Quantum Mechanics (QM). The basic idea, and I am (over)simplifying here, is that there are an infinite number of universes, with a new universe being created each time we make a decision or take some kind of action. For instance, in this universe I got out of bed, worked on my new piece of animation, took the dog for a walk, shipped my defective TiVo back to TiVo, ate lunch, took the dog for another walk, moved my bowels, drank a Starbucks mocha frappucino, and sat down to expound upon the theory of the MWI of QM. However, what if I didn't get out of bed until until five minutes later? Well, in another universe, that's just what I did. Maybe I moved my bowels before I shipped the defective TiVo back? Yes, that's just what I did. In another universe, I never bought the TiVo in the first place. That is a terrible universe, and I'm glad I don't live in that universe.
But the "me" that lives in that universe in which I didn't buy a TiVo actually likes that he doesn't have a TiVo. He's probably one of those jerks who tells you that you shouldn't watch television at all, that it stifles creativity or whatever other unpleasant things those TV-haters tell you. The life he's lived and the decisions he's made have made him a person unrecognizable to me.
Physicists have two ways of looking at the the MWI. Some take a realist approach to the theory; that is to say, they actually believe that each of these universes is physically real. Others believe that these other universes are just abstract concepts, and that there is nothing real about them. (John Bell called the idea that each of these universes was actually real "grotesque.")
As a layperson with absolutely no idea of what I am talking about, I am excited by the idea of an infinite number of "mes" out there loose on the various "alternaverses" (my word). The prospect of meeting some of these other mes is an enchanting one, filled with fanciful possibilities. What I am saying is, I would like to have a three-way with myself. Not that other me who doesn't like TiVo, but the other me who went into banking. He is very successful, and that is a very attractive quality. Or, going back even further, the other me who was created when my father met a French woman, and I was born a girl. Man, oh man. Can you imagine me as a half French woman? I bet I would be so uninhibited! I would have such a filthy mind, and no shame whatsoever. Butterflying, trapezing, joyeux du oignon... nothing would be too much for that me. I hope that me was born in like 1985 or so, because then she would be the perfect age.
In conclusion, the Many Worlds Interpretation of Quantum Mechanics is highly controversial, and as of this writing there is no way the theory can be tested. Until that day, I will continue to fantasize about having a three-way with myself.