h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

You have all done this.
You finish washing up and know that the bowl is empty. So you tip the bowl up and low and behold there is a spoon there, which clatters into the basin. This is the work of Kitchen Sink Gnomes who add that extra spoon when you are not looking.

Kitchen Sink Gnomes live in the U Bend of your sink. This is why it is always so mucky when you need to mess with it. They attempt to resist any disruption to their house by spraying you with water.
The spoons are aquired from office kitchens, which is why there is never a spoon for stirring your morning coffee.
Kitchen Sink Gnomes find this joke hysterical and never tire of doing it.

Are these also the gnomes that put very sharp knives in the sink to cut you with, even though you know that you haven't used any or put them in the sink.

Good point. I'll add it, thanks. I think they also pile up dirty washing up on random tables when you've just finished washing up and think you've done everything.