From Star Trek's Mirror Universe to Family Guy's multiverse, one of the staples of sci-fi has been the dimension in which alternate (usually evil) versions of ourselves exist.
Not so far-fetched, as it turns out: The Massachusetts Institute of Technology now says that there's a possibility, at least theoretically, that life exists in theorized alternate universes.
... Cosmologists speculate that a multitude of other universes exist, each with its own laws of physics. Recently physicists at MIT have shown that in theory, alternate universes could be quite congenial to life, even if their physical laws are very different from our own.
In work recently featured in a cover story in Scientific American, MIT physics professor Robert Jaffe, former MIT postdoc, Alejandro Jenkins, and recent MIT graduate Itamar Kimchi showed that universes quite different from ours still have elements similar to carbon, hydrogen, and oxygen, and could therefore evolve life forms quite similar to us. Even when the masses of the elementary particles are dramatically altered, life may find a way.
(Nice, MIT alludes to Jurassic Park.)
Some physicists have theorized that only universes in which the laws of physics are "just so" could support life, and that if things were even a little bit different from our world, intelligent life would be impossible. In that case, our physical laws might be explained "anthropically," meaning that they are as they are because if they were otherwise, no one would be around to notice them.
You can read a lot more at the official MIT Web site.
Still unanswered: Why do the evil versions of ourselves have goatees?