The Exchange is one of the most glorious and under-used unwritten law of partying. It just states that if you hold back the hair of a female, while she is projectile vomiting into the toilet after a few too many, She must immediately slob on your knob, during, or after throwing up.
Shit motha fucka that bitch threw up on my lap so i made her suck my D.
Bonnie and I were having a wonderful time at the party until she got sick, then she had to suck my penis. I sure enjoy calling out the exchange.