Penny: Wait, why are you being so weird?
Sheldon: It occurred to me that perhaps you were telling the truth about Bill Gates and it wasn't just part of an elaborate prank.
Penny: What would the prank part even be?
Sheldon: I show up to meet Bill Gates over your "objections," but it's not Bill Gates at all, no. It's one of those look-alikes that you hire for a party. And then when I go around showing everybody the balloon animal that "Bill Gates" made for me, I'll look like an idiot.
Penny: Have you been eating laundry detergent?