The act is successfully performed when a woman is sitting in the toilet facing backwards and taking a shit while giving a man a grumpkin while the man is taking a shit in the tank (an upper decker).
Best performed on a public toilet, "friends" toilet, or at work.
The reverse technique with the woman recieving head on the tank from a man on the toilet is referred to as a cookie monster.
Dude B: Great, I talked my wife into a Snuffalouphagous on Saturday. She wanted a Cookie Monster on Sunday but I said no way.
Dude A: Word