We had a birthday celebration for Gary at work today. Neither of these guys is Gary; in fact, I think they just showed up for the cake.
Our office has one or more of these little celebrations every month. We sign up for a person at the beginning of the year, then our secretary reminds us by email a few days before the birthday. Our job is to get a cake or equivalent dessert item and a card. We circulate the card in an unmarked manila folder for people to write notes and signatures. It never a secret, but everyone pretends it is, so we all gather in a room, then send out for the birthday person. When s/he arrives, we sing (for lack of a better word), then cut the cake, eat, hang around for a while, then go back to work. Truly a cherished tradition.