The Convention Conundrum - S7-E14
Sheldon Cooper: [sneaking up to a house] I don't understand what we're doing.
James Earl Jones: Shhhh!
Sheldon Cooper: Whose house is this?
James Earl Jones: Carrie Fisher. And she's a little crazy, so get ready to run.
[He rings the doorbell, and they run for it.]
Carrie Fisher: [storms out with a baseball bat] It's not funny anymore, James!
James Earl Jones: Then why am I laughing?
Chosen answer: It does. The variable cleanliness of the cab and the habit of taxi drivers to engage customers in small talk would be too much for Sheldon to handle, and not an option for him.
Captain Defenestrator