It's OK, you don't have to give me anything in return. –Of course I do. The essence of the custom is that I now have to go out and purchase for you a gift of commensurate value and representing the same perceived level of friendship as that represented by the gift you've given me. It's no wonder suicide rates skyrocket this time of year.
I got you and Leonard a few silly neighbor-gifts, so I'll just put them under my tree. –Wait! You bought me a present? –Uh-huh. –But why would you do such a thing? –I don't know, 'cause it's Christmas? –Oh, Penny! I know you think you're being generous, but the foundation of gift-giving is reciprocity. You haven't given me a gift. You've given me an obligation.