Ezra has two white cups and two identical electric-blue superballs.

Ezra: “I’m going to mix these up, and you’re going to find which one is where.”

He mixes for a while. He lifts up one cup, takes the ball, and pulls it up his sleeve. He cranes his head around to look at this, then (reluctantly) puts the ball back under the cup. He mixes the cups more.

Ezra: “OK. Now where’s the ball?”
Carrie: “There.” (Points at one of the two cups with a ball under it.)
Ezra (archly): “But which ball is under it?”
Carrie: “I don’t know. The look exactly the same!”
Me: “The left ball.”
Ezra: “The left ball?”
Me: “Yeah.”
Ezra: “Nope! That’s wrong! I was paying attention.”

Later, using three cups and three corks:
Ezra: “OK. This is really hard. So I’ll make it easier for you: I’ll tell you the most obvious one, and you tell me if that’s the right one or if I’m trying to trick you.”

Still later with three corks, the rules are that Carrie must close her eyes and cannot look at any time; neither during the shuffle nor at the end when she’s trying to pick.
Ezra: “You tell me which cup you want to pick, and I’ll look under it.”
Carrie: “Uhhh, the right one.”
Ezra: “Which one’s the right one? Can you point to it?”
Carrie: “No, because my eyes are closed. I don’t know where it is.”
Ezra: “OK, I’ll look under this cup for you. Is this the cork you want?”
Carrie: “I can’t see anything. I don’t know which cork that is. Sure?”
Ezra: “Nope! You picked the wrong cork!”