Found a full-to-the-brim, giant, plastic tumbler of water in the middle of my kitchen floor at 3am.
It was so full, it had that little surface tension rise above the glass' lip.
Definitely wasn't there, when I went to bed. It was a few feet from any counter or table. Could not possibly have fallen down that way. No water leaks from ceiling. Smelt like water.
I was the only one home (my partner was in another country), doors were double-locked and alarm was on. I was sober, had just woken up and went for a glass of water, coincidentally.
The dog refused to come into the kitchen until I put the glass in the sink. Very odd behavior for her.
Never happened again. Truly WTF.