omomg

character who humps a towel/blanket/pillow to help them hold, leaking constantly, and when they finally manage to pull the towel/blanket/pillow out from between their legs there's a big noticeable dark spot on the fabric.

character doing that desperate speed walk toward the nearest bathroom but they're already full-blown pissing themself and there's a trail of wetness on the floor following them. (bonus if it's all uneven and zig-zag shaped because they can't walk straight, or has some noticeably larger puddles from when they stopped and tried to hold themself or cross their legs.)

character bottoming or receiving during sex, needing to pee really bad, and the damp patch on the sheets gets bigger and bigger in spurts.

character on a long drive finding a gas station or rest area to pull over at and thinking they just barely made it in time, but when they come back to their car after the fact, they see an obvious wet spot on their car seat.