Chimera. As in the human medical sense of the term, how physical is it? A set of frateral twins are in the womb and one "merges" into the other. Is it just the set of DNA or are there physical bits in the fully developed twin? I can remember reading something about a woman having her twin removed from the back of her throat. The twin was something akin to a small lump of teeth, but is this the same thing?
Just trying to clarify. :)
Edit: Wow, thanks everyone. This certainly helps me out. :)