You face your partner and say a word, then your partner says another word. Then, you turn to a third person (or persons) and say the two words together. The first person to fall down laughing loses.
It is best if you think of the two Siloughettes from Seasame Street.
Person one: Sick
Person two: Dick
Turn to audience, together: Sick Dick
The equivalent of Maniac/Heavy difficulty in the game Dance Dance Revolution 3rdMIX, a piece of shit that I can't believe some people stil obsess over.