I was invited to a foursome, never actually did that.
My friend jeremy and his wife caught sight of my girlfriend who they thought was hot. Both were/are bi chicks. Jeremy started trying to sell me on the idea of it by telling me the ettiquitte of the 4some, trying to get me into it. I never took them up on it, because I saw them all the time, would probably laugh or something the next day, all of my friends however were trying to get me drunk so that I would do it . But, since I haven't seen them much lately I'd go for it if they wanted to.
fun times, i loved college