How to behave at an office party

My last posting talked about the many office holiday parties bestowed upon me, much to my pleasure indeed. I must comment on the differences in these parties: Stuffy (formal) parties, and carefree/wild (informal) parties. All of our parties are catered and have an open bar, but depending on the invitees the atmosphere can make for a long night or a crazy night! Our most recent holiday party - crazy, very crazy!! Depending on your position on behavioral actions during such events, our most recent party would impress you or offend you. My stance, impressed of course! For me it is very enjoyable to watch people let their guard down, drop the jacket and tie and let loose especially in a corporate setting. This is exactly what happened most recently. Libations were flowing, crushes were revealed, habits were discovered, etc. In other words a very fun and revelatory time. I tend not to stray too far from my 9-5 demeanor, even after 5:00. One of my coworkers was offended and decided to make it a short-lived evening. I, myself wanting my beauty rest made it home at a reasonable hour, but I hear not too many of my coworkers followed suit. I hear the holiday party made a long long night for many people. Makes for an agonizing work day the next day!