Merry Christmas!
Where I work there is a single Christmas Party each year for all the Sydney staff (about 1,000 of them), rather than each department having their own party. The venue and "theme" are usually kept secret until a Flash based invite goes out to all staff via our Intranet, whose purpose is to reveal both and provide a way to RSVP. This invite is usually done by the company we use for all of our web graphics work, however this year I was asked if I wanted to give it a go.