Patron: pops up on other side of book shelf, stares at me through the shelf
Me: *continues to shelve*
Patron: leans forward, widens eyes into bug-eyed stare
Me: *raises an eyebrow* "May I help you, sir?"
Patron: *begins laughing and grinning* "Naw, I'm just messing with you!"
Me: "I work in a library, sir. You have to do better than that."
Patron: "Now you're scaring me."