Quack

Thing Two (while playing doctor): Here you go. Take some of this.
Me: Is this medicine?
Thing Two: Yes.
Me: Oh, good. I should feel better soon.
Thing Two: No, you won't.
Me: Why not?
Thing Two: It's poison.

Bedside manner

While playing doctor, Thing Two lays on a box that is supposed to be the examining table.
Thing One: You have a baby in you, and I'm going to cut your belly open with a sharp, sharp knife.