DH and I escaped one year right before Christmas to Puerto Vallarta. It was a desperately needed vacation and scheduled last minute. It was soon before I ended up leaving Job From Hell in 2007.
We had a friend of ours who was recently divorced. He had moved into an apartment close to us. He was also the worst dog owner ever. We asked him to house sit, being able to use our backyard (he had moved into an apartment so dog couldn't run free), take care of the cats, take advantage of our Internet connect, games, etc. Seemed like a good deal for us and him.
At the same time, we still had this cat named Loki, who peed on everything. We warned friend of this, but apparently it didn't work.
We open the door after a blissful week in Puerto Vallarta and I am SLAPPED in the face by the stench of cat piss. That cat had peed all over multiple items in the house and somehow friend didn't notice. Or clean it up. The house wasn't messy really, but the cat had peed on the stack of mail, a towel left on the kitchen counter, etc. I had to work really hard not to scream at friend, who was appropriately apologetic and bashful. So, DH and I had to clean house for about 3 hours, sniffing out all corners to make sure it was clean again. Friend did offer to help clean, but I really needed him to just get the hell out and I think he realized.
Loki went away about a week after that. He can pee wherever he wants now, b/c he is a good barn cat. I felt bad for him, he was a rescue who obviously didn't have litterbox training and just wasn't getting it. But he's hopefully happier now and so are we.