OK! Mystery Solved! On Wikipedia, which we ALL know is the most authoratative source on the net
XD, it says that while Jack is in Davey Jone's locker (the sandy place in the trailer), he is confronted with many seperate aspects of his character. Meaning that he probably has visons of his past or what might have been his past. So seeing as how if he had joined Jone's crew, he woulda looked like this, he probably dreams himself looking like this. I'm guessing that during the scenes where the crew is traveling the frozen ocean, we flip back and forth between them and Jack, and Jack is having these visions.
Bagder, I'm afraid that you are all wrong... Hah.
