Do you know of any books, shows, or movies about people who have a darker half?

Question: Do you know of any books, shows, or movies about people who have a darker half!?

not a darker half inside of them but as a separate being!. I'm wanting to write a book about someone like that but I don't want to copy people!. I know Yu-Gi-Oh does but I'm going to try and do it different!.Www@QuestionHome@Com

Best Answer - Chosen by Asker:

Kevin Costner was in a movie a couple years ago called "Mr!. Brooks" in which he has an alter-ego who is a serial killer!. The alter ego, played by William Hurt, is sort of an imaginary friend, I guess!. Mr!. Brooks can see him and converse with him, but of course no one else can!. So it's Kevin Costner's character, not Mr!. Brooks, who performs the killings, but it's the alter-ego character who urges him to do so and feeds his addiction to murder!. Surprisingly, the character of Mr!. Brooks, despite his being a killer, is actually fairly sympathetic!.Www@QuestionHome@Com

Blackwood Farm by Anne Rice - http://en!.wikipedia!.org/wiki/Blackwood_F!.!.!.

Doppelganger (movie) - http://www!.imdb!.com/title/tt0106753/

Additional info here: http://en!.wikipedia!.org/wiki/Evil_twinWww@QuestionHome@Com

The tv show Dexter is about a criminologist who is a serial killer!. He kills criminals who are guilty of heinous crimes but get off due to lack of evidence!.Www@QuestionHome@Com

Stephen King the dark half!.!.!.it was made into a movie also!.
Dr Jekyll and Mr Hyde thing
The list could go on and on this is a popular theme!.!.!.!.Www@QuestionHome@Com

You mean like Dr Jekyll and Mr Hyde!? Or the characters of Nicki/Jessica in the TV show "Heroes!?"Www@QuestionHome@Com