Originally posted by Raisen
I agree although I don't consider Hulk's physiology PIS. He has a long history of resisting transmutation from characters like the Grey Gargoyle and given how he has been shown in the banner head/hulk body configuration and vice versa, i'd say it's indicative that Hulk is somewhat of a shape shifter. Even the way he gains mass is indicative of this. I think Iceman loses this hard.
But freezing is not transmutation; it actually just amounts to removing heat energy from a system. Iceman in essence would be attempting to drain the heat from Hulk's body. When the possibility of Iceman freezing the Earth is mentioned, what it is being referred to is an ability to drain heat energy on a global level.