A Bag o' Beagles
A bag of beagles is when your butt is so wobbly it looks like it’s been filled with tiny dogs and they’re trying to escape.
Her butt looked like a bag of beagles that just got the door unlocked.
He looked like a bag of beagles that had a tiny jailbreak.
She sat down like a bag of beagles trying to dig their way out.