It's sort of a cliche at this point, stories about "ca-raaaazy" office holiday parties gone awry or whatever. But cliches usually exist for a reason, and in this case, the reason is that people really do tend to go apeshit at their office parties. It's the one time of year the thin veneer of propriety comes down between you and the people you spend, oh, a good 50% of your time on this earth hanging out with in order to make enough money to survive.
Which can be a really fun time to relax and get to know the people you work with in a somewhat more real way! Or an opportunity to get yourself fired for a public sex act, which actually did happen at my friend's office last year. Terrible. Before you start swilling eggnog with the interns, maybe brush up on a few ways to get through the whole thing and remain employed (and maybe have some fond memories, if you're lucky).