Revenge!!!

Ok, so I travel a lot, and my sister and her husband are usually kind enough to house sit and guinea pig sit for me. Sweet right? BUT here's the thing, there's always...ALWAYS some sort of prank awaiting me when I come back home: they'll teepee the living room with party streamers, silly string ALL over the bedrooms, replacing my charmin ultra soft toilet paper with generic 1 ply toilet paper (aka sand paper), things that they know REALLY irk me. And I know, I know - it's all in good fun. But THIS time, the tables have turned. They have to go out of town because they are hosting a couples/marriage seminar sponsored by our church, and guess who's house sitting for them? Guys...I'm taking revenge...and I need your help with ideas of what to do to get back at them 😈😈😈