What's the weirdest thing a guest has done while at your house?

My answer. Summer before last a good friend of mine came to visit with his kids and his wife's brother (wife had to work). They were only there for lunch, maybe 3 hours, then took off. The time is an important detail in this story.

His brother-in-law had previously been diagnosed with schizophrenia (I think?), but was considered high functioning and on meds. Nice enough guy, hadn't met him before. He mostly stayed in the dining room/library the entire time, looking through my books...which I did find a bit odd. But I knew from my friend that he had social anxiety, do to this condition, so I wrote it off.

A few days after they left, I went to go look for a book I was going to reference. I'm a stickler for my books being organized. Couldn't find it. Ask my husband if he messed with the books. Nope.

As I inspected further, I realized the entire right side of my bookshelf had been rearranged. Somewhere, in the space of 3 hours, ~1.5 of which he was in my presence, he managed this.

It still gives me a good laugh.