“I’ll get you for this, you punk. You ain’t heard the last of Joey Catheter!”

Pee in the squirt gun to make it realer and so you can pee someone else’s pants

I spilled water on myself once when I was eating alone at a restaurant, but luckily my pants were a material which dried easily after some time. But I had alresyc eaten, and had to sit there with a napkin on my lap and order an espresso 😅

This seems like a doable prank. If you don’t over saturate, you could probably do it with the other person noticing.