p.o.y.s.
You’re so full of pee you look like you’re about to burst
He was P. O. Y. S. ing in the hallway and looked like a water balloon about to pop.
She P. O. Y. S. ed in the middle of class and got kicked out.
My dog was P. O. Y. S. ing on the couch and it looked like he was going to explode.