Every now and then, especially on a slower night, we'll do a round of "Kamakaze Karaoke". There are numerous ways to run it, but what I usually do is as follows:
1. Randomly assign each active singer on the list a number.
2. Ask a performer to pick a number between 1 and whatever the highest numbered singer is.
3. Ask another performer to pick a number between 1 and whatever the highest number disc is.
4. Ask another performer to pick a track number.
Then whatever singer was picked sings whatever song comes up as that disc and track. Anyone not performing the song owes a round for all the singers if they fail to sing the song.
It can get really fun at times. Its also another way to come up with some decent songs you may never have considered. And to be quite honest with you, I never have had a singer refuse to sing a kamakaze song. Therefor, never have they had to buy a round.