We like to think that there's a sort of conduct standard for all houseguests. But it only takes one houseguest to make us realize that it's the jungle out there, baby. And the worst time to realize that people are filthy animals is when that jungle is your home. It's hard to forget a rude and annoying thing a houseguest does, maybe because we feel so disrespected and inconvenienced when someone gleefully brings their crap personality into our private lives. Also, it doesn't help when someone leaves after cracking your toilet in half like they're the King Solomon of pooping.