I've noticed that there is a currency called "FUN."
I do not know how to obtain FUN, but you can spend it on a lottery/drawing type thing. So far, I've gotten +50% EXP items and a store front that I can put in my apartment. It seems that items I put on the AH show up there. I'm not sure how to open the apartment up for other people, however, so this may just be a 'kicks and giggles for friends' thing.