Chinese musical chairs! Everyone brings a gift and places it in the middle. Everyone sits on a chair. Then one person grabs something from the pile and opens it. The next person can either steal that person's gift or get something from the middle. And it keeps going. Once a gift has been taken three times, it is dead and can no longer be stolen. it's really fun.
I forgot what it was called, but you make the birthday person leave the room. This game is a prank so it can be done only once. You explain to everyone else that you're going to ask the birthday person to solve a murder/ other mystery. You tell them that the birthday person can only ask yes or no questions. If their question ends in a vowel, no matter what the question is, you all say yes. If it ends with a continent, you say no. If it ends with a y you say some times. You bring the birthday person in and tell them there was a murder/ mystery thing and tell them they have to ask yea or no questions to solve it. When they think they have the answer, they must ask it in a form of a question, or else you can't answer.