A classification of girls that enjoy anal sex, which was found out by the following:
In midst doggy-style sex, if the man pulls out and quickly goes for anal sex, and pumps away very fast, and instead of waiting for the classic angry dolphin, and the girl utters loudly "YE-E-E-E-E-E-E-E-E....-S" in a goat voice, then the girl is classified as a happy goat, telling the guy that she is a fan of anal sex.
"Dude, you remember that redhead from the bar last night???
So, apparently, she makes a crapload of money, looks amazing naked, her carpet matches her pubes by the way, and best of all...SHES A HAPPY GOAT!"