Past or present, real or not too (I suppose). Who would you choose?
For me, I’d pick none other than Sheryl Cooper, so I could be welcomed to my own personal nightmare by Alice every single night. 
< happy shuddery sigh >
Your turn!
Trade places with them for how long?
For as long as you wish. In my case, she’d never get to come back.
< BWAHAHAHAHA! >
Wonderful. I pick George Clooney (even though I’m not a guy). I don’t believe for one second that guy is stressed out about anything. He may very well be, but oh man, can he sure fake it.
Do I get their body and skill set, too? If so, I get dibs on Amy Adams! She’s just so friggin’ cute, and I love every single role she’s chosen - even the ones in terrible vehicles. I think (hope) she’s still on her way up, and I’d love to experience life as a *talented *starlet.
(Holy $#!&! I just realized she played Tara’s cousin in the “Family” episode of Buffy!)
Of course you get to keep everything! Or at least I hope so… that chick is beyond hot at 51 and she’s a dancer!! I so don’t have the body for that and to be able to pull off those sort of moves would be just another version of my heaven.
Workin’ up a sweat indeed. 
Ossam bin Laudin, circa 1990. Then I would kill myself.
I’d be Taylor Swift and spend the entire time either in the shower or in a room with a video camera and a mirror.
Bill Gates. I’d write a large check to RiverRunner and switch back.
RR
Angelina Jolie.
There’s Brad, a nice family, the good works, nice paycheque and perks, and she’s hot!
Well, all the good topics - money, sex, destroying one’s enemies - have already been riffed on, so I will go with a serious answer and pick Alex Lifeson. It would be awesome to have his guitar skills. And hey, maybe once I come back, I will retain some of them.
Either that or whoever gets to bang Lena Heady
I would swap places with my boss, then soil myself at my desk and just sit there long enough for a few people to notice. And then swap back.
Assuming I’d take on the person’s mental characteristics, probably I’d trade places with my sister.
She travels a lot and goes to cool events and hangs out with fun, sprightly, light-hearted people.
Unfortunately, as myself I don’t have the mental or emotional energy to be really consistently social;, and travel of pretty much any kind (especially overseas) just stresses me out. However, if I were she it wouldn’t bother me!