A Bag o' Beagles
A bag of beagles is when your butt looks like it's been stuffed with tiny dogs and someone took a hammer to it.
His butt looked like a bag of beagles that just got hit with a bat.
She looked like a bag of beagles that got trampled by a herd of elephants.
He walked in like a bag of beagles that got kicked by a very angry goat.