DARK JACK WAS CANON!!

OMFG.

Dark Jack was canon at one point in the development of the Rise of the Guardians movie!

And not even when Pitch asked Jack to join him in Antarctica, but actually BEFORE Jack was chosen as a Guardian!

Wiki tells all.

"The team also toyed with an idea for Jack's back story, he and Pitch could have been like brothers. Jack could have been a bad guy but he and Pitch had a fight which cost Jack his memory, and giving the Guardians reason to not trust Jack."

Here is the link if you don't believe me:
riseoftheguardians.wikia.com/w…

No wonder Cold and Dark go so well together