Season 9, Episode 23: "The Finale"

-State your name. -Bookman. Joe Bookman.

-And what's your occupation? -I'm a library cop.

What's a library cop do?

We chase down library delinquents.

Anyone in this room ever delinquent?

Yeah, he was. Right over there. Seinfeld.

-How long was his book overdue? -Twenty-five years.

We don't call them delinquent after that long.