Mad Piss
When you feel like your bladder is about to explode and you can't wait to pee, no matter what you're doing.
I was in the middle of eating a taco and I had to run to the bathroom like a scared rabbit.
During the final round of the spelling bee, I had to pee so bad I almost spelled 'pissed' wrong.
I was trying to text my crush and I had to pee so bad I sent them a whole paragraph about it.