So, we know who we WANT to get punk'd, but i don't think their managers or lawyers let them sign the waivers. So many people have said like Hugh Jackman, say that they are that relieved that its all a joke, that they sign whatever is in-front of them without really knowing it, Hugh was just so thankful its was fake that he didn't care what he was doing.
So my point is that Britney Spears has had a contract since season 1 not to be Punk'd, we can be sure that Demi has the same contract, Ashton himself can not be punk'd (see season 1, Britney spears ep).
Who do you think will never be punk'd?
I think Paris Hilton will never be Punk'd as her reps wouldn't allow it i reckon. Donald Trump wouldn't, as he doesn't want anyone proving he is an idiot.