Jack

Jack is Mike Dawson's only friend. He is a stereotypical 1950's greaser, and he rides a motorcycle. He sometimes helps Mike make sense of things. At the end of the game, it is revealed that Jack is the shape-shifter, as well as Mike Dawson's Dark World counterpart. However, it is also implied that Jack is an alternate personality of Mike's and does not exist at all. It isn't clear, though.