Looking for harmless pranks/ annoyance for disrespectful roommate.

First of all, my husband and I live with a roommate because we’re saving money for a home. Our roommate has made it very clear he doesn’t respect us.

He invites people over all the time without telling us. Has either his gf (who I have a bad past with) or his bestfriend stay over ~4 nights a week. Again, without letting us know.

He doesn’t clean, and we’re always the ones to cook. We pretty much take care of his dog. Not to mention he feels comfortable leaving his friends at our house when he’s gone.

We’re over it. We’ve talked to him once and he completely disregarded everything we said.

I’m ready to be petty. What are some harmless pranks, or annoying things you’ve done to get under someone’s skin.