"Oh, for sure, two livers."
"I'd want another pair of lungs, 'cause I'd be able to run for hours and hold my breath underwater forever."
"Two hearts. I feel like I'd never need to sleep again if I wanted. Two brains sounds like it might be horrible and confusing."
"I'd want two brains, 'cause then I'd be double-smart."
"Two hearts for me!"
"I'd definitely have two brains. Hopefully, I'd be able to multitask better."
"I'd take two brains, 'cause I'd be more conscious."