Earlier this year I had the same experience at my senior prom. I went to the afterparty and drank quite a lot (~4 miller lites, 3 shots of Bacardi, and some liquor.). I've drank mildly in the past so I know that I'm (somehow) more of a heavyweight drinker, especially given my size. Though, this was the first time I was legitimately drunk. Surprisingly I can keep my cool and am completely aware of all of my actions; Most people couldn't even tell I was drunk. I was able to stop myself when I knew things were getting out of hand. (i.e. my balance started getting worse)
And then the cops showed up and talked to the host's parents (yes they were there) because apparently someone got into an accident down the street and told the police where they were heading. So all ~70+ seniors from my school had to cram upstairs in bedrooms, bathrooms, hallways, whatever the crap we could find until the cops left.
Then after that, the host student and her parents began enforcing the: "You're not leaving until tomorrow because the cops are patrolling our street and that'd be probable cause to come in" rule. So we all had to stay overnight (which we planned on doing before, but we weren't being /forced/ to)
All in all it was definitely a fun night. 2 girls were hitting on me for most of the night and I'm like 'nop' (ha, girls). I ended up falling asleep with my 4 other buds (two of which are female) in a fairly awkward position on a windowsill.
edit: holy forget that was longer than I thought it was. +1 to anyone that reads it all O-o