We've moved house and we have a kitten who is using a litter tray. We used to put it by the back door but it isn't an option here so it's in the bathroom which is downstairs (seemed sensible).
A couple of points:
Our kitten likes to kick the contents of her litter tray out of the tray itself and onto the floor, especially at night. Generally speaking it's me that cleans it up as apparently it is invisible to everyone else 
We've fallen behind on the laundry with the move and wet weather so the basket is currently over flowing in the bathroom.
Anyway, I worked all weekend so was out or dashing around from Friday until Sunday night. DD was at XPs and DH was having a weekend off I think (it's about time really but thats another post lol)
On Sunday morning, whilst weeing before running out to work (sorry for visual) I looked around my bathroom. There's laundry spilling out everywhere, no towel and the kitten had done what she does best. Everything needed sorting, but I didn't have time.
Before anyone starts bashing DH, yes he could have done it, but he didn't. Really I'm not fussed, it's not an issue, he needed a weekend off and I'm not down trodden or taken for granted.
Anyway...when I get home DH tells me that when xp arrived he let himself in (DH was upstairs) and allowed his girlfriend who we're told has 'loads of OCDs' to use our bathroom without asking (wtf??? Again that's another post).
I thought I couldn't feel more mortified.
Then he adds "and I'd just used the last of the loo roll.......and I think the bathroom was erm...quite smelly too"
Shall I wait for a letter from Social services or just call them myself? lol