Leonard: So, how do you two know each other?
Missy: He once spent nine months with my legs wrapped around his head.
Leonard: Excuse me?
Sheldon: She's my twin sister. She thinks she's funny, but frankly, I've never been able to see it.
Missy: That's because you have no measurable sense of humor, Shelly.
Sheldon: How exactly would one measure a sense of humor? A 'humormometer'?