Sheldon Cooper: I realized if I find the other people who checked out the book, they’d be looking for friends, too.

Mary Cooper: That’s really smart.

Sheldon Cooper: Missy thought of it.

Mary Cooper: You’re kidding.

Sheldon Cooper: I’m as surprised as you are.

From Young Sheldon – Season 1 Episode 2: ‘Rockets, Communists, and the Dewey Decimal System’ (1×02)