There are three major rules in writing that we should always follow. These rules aren't really talked about because they're kind of obvious. And if you break these rules you're not smart, you're not clever, you're not subverting expectations. You're just an idiot.

Rule number one: Characters DON'T go to the bathroom

You'll never see a screenplay where the protagonist simply goes to pee. 

Rule number two: You must pay off what you set up 

This goes for everything. Jokes, props and sometimes little pieces of dialogue.

I'll write a third rule some day...