When we were kids, the attic snatcher used to come and take toys that were left out on the floor while we slept. She didn't come very often, but she came without warning, as I recall. It's one of those things that you hated as a kid, but once you become your mother, er, I mean, A mother, you realize the brilliance of it all.
My kids are still little enough that I warn them when she's coming to our house. And they know it's me, because I really don't want them to develop any nightmare issues - that would be worse than a messy playroom. And, really, I use it as a reason to get them moving to clean up their toys. And to flush out the ones they really don't care about, because they are lazy enough to say "whatever" to a toy and not bother to clean it up.
She's actually only had to come once, but I've used her several times as a threat (oh, say, today) to get them to clean up their toys, just so I can please, please, please vacuum! And, if there's any random toys laying around, they are MINE!
Oh, and the toys that the attic snatcher got when I was little? We usually got them back, from the attic, of course, after a period of desperation and room-cleaning. But, once, much later after we'd moved, my sister and I discovered a box in the garage, brilliantly labelled "attic snatcher." There were toys in there that we hadn't seen for YEARS.