I'm a Sagittarius myself, and I...actually, I don't really know what it means to be a Sagittarius, other than I was born between November 22 and December 21.
BUT...
My username, Winslow Leach, can be described as a Gemini (I think).
Ya see, in De Palma's Phantom of the Paradise, Winslow Leach is the naive young composer whose music is stolen by an evil rock impresario. Leach is accidentally disfigured in a freak accident, and becomes the Phantom. Gone is the sweet, lovable fellow we met at the beginning of the film. Now he's a determined, mad creature prowling the shadows of the rock palace the Paradise, seeking vengeance.
Actually, a lot of De Palma's films deal with doubles and dual identities. There's even a website out there called Double De Palma, which describes, in detail, the dualness of the characters in his films.