Penny: Hey, guys, the building manager said the reason the power went out is someone went down into the basement and just pulled the main breaker switch.
Leonard: Really. Who do you think did that, Sheldon?
Sheldon: Oh, I don't know. But whoever that mystery man was, you should be eternally grateful, for without him, there would be no Leonard's Day.
Penny: Leonard's Day?
Sheldon: Oh, no pressure. Just get him a crummy card, you're good.