The memory of a pussy. When a pussy gets gets a dick, it has a memory/attachment to that dick and likes to be fucked by that dick. If a pussy gets fucked by a strange dick it forms a new pussy memory and now wants to be fucked by THAT dick.
Bro 1: Wow man I made that chick we met at the party cum all over my schlong! But it smelled weird...
Bro 2: Yo, you are fuckingdisgusting!!!
Bro 1: Huh?
Bro 2: That brawd had a dirty filthy cunt. That was pussy milk.
Bro 1: Oh God!!!