What did one skeleton say to the other when he was lying and how did the other skeleton reply to the first skeleton?

Papyrus: Sans, I know you're lying!

Sans: No you don't

Papyrus: Yes! You're socks are still on the floor!

Sans: //looks at them, shrugs// I picked them up

Papyrus: Sans, you're obviously lying!

Sans: Are you sure?

Papyrus: Yes, I'm sure!

Sans: Are you sure you're sure?

Papyrus: Y- //stops// ...uh...