Metamimic

Metamimic: [Major] by Iczer

'Oh yeah...part of the mutant elite...'

The character can alter in response to others, gaining the advantages of their unique structure. While he does not gain any new actual powers, he does become more like those he emulates.
The character merely selects a target within 60 feet and makes the change as a single melee action. He gains all the targets unnusual characteristics, physiological modifications due to unearthly environment, side effects, Mega Hero special abilities, and so forth. and he can keep them for up to a week before requiring re-exposure (can dump the benefits earlier if he desires.)