You need equal numbers of guys and girls, and form a team of each. You can ask girls to join the guys team if required and vica versa.
Write all your guests names onto pieces of paper and give one piece to each guest. You become whoever your piece of paper says you are - do not disclose this.
Everyone sits in a circle, alternate guy, girl, with four people on the couch and the rest on chairs. Have one extra, empty chair.
The object of the game is to get all your gender onto the couch. The person who is sitting with the empty chair to their left calls out a name, trying to get the opposite gender off the couch. The person with that piece of paper must stand up and move to the empty chair. They then swap their piece of paper with the caller. The next person to call is the one with now empty space to their left.
For example, say that Jane calls out "Bob". Joe has the name "Bob" on his paper so he moves to the empty chair and exchanges papers with Jane. So Jane now becomes "Bob". The person who was next to Joe now has an empty space on the left and is the next caller.
This goes on until one team has 4 of their own players on the couch.
This is hard to start because you don't know what name everyone has now got - it does get easier. A real laugh and fun for all ages.
Click this animated image!