20
Now the answer prompt and the box prompt are asking different questions. My best birthday party was when I turned 20. There was a huge party with tons of friends, and to this day I sometimes meet people who I later learn were at that party. Drunken debauchery was the order of the evening, and we did it well. It was supposed to be a black and white party, but that quickly died as the party rolled on. I was quite sick the next day.

8
The year I turned eight I had a party with everyone in my grade at school. A boy girl party, because I had too many friends to have just a boy party. It was pirate themed, as only the best parties are.