When your friend goes to the bathroom, and you start hitting on the girl he was with.
Dude, Ryan just went to take a dump. Watch the door while I pull a Poop 'N Scoop?
When you're not wearing deodorant and your friend is, so the two of you scissor with your armpits.
Omg Mary I totally forgot deodorant. Scissorpit me?
When you and your friend both have to poop, so you fartpool to the bathroom.
The kids have to go #2. Would you mind leading the fartpool today?