Quote from The Big Bang Theory 10x05 Sheldon Cooper: When I opened the door, I saw my father having relations with another woman. Penny Hofstadter: Oh, that's awful! Sheldon Cooper: I know. It's also why I never open a door without knocking three times. I mean, the first one's traditional, but two and three are for people to get their pants on.
Quote from The Big Bang Theory 10x05 Sheldon Cooper: Amy Farrah Fowler, will you share this toothbrush holder with me? Amy Farrah Fowler: I would love to. Leonard Hofstadter: Did we really need to be here for this? Penny Hofstadter: Call me crazy, but I found it moving.