When night falls and everyone in your house has gone to sleep, your couch sneaks out and goes swimming. It doesn't want to get wet, so it wraps itself in a waterproof suit, then swims the underground waters to find a fountain and settles on the bottom. All through the night, people toss coins into the fountain. Some make wishes, but most only want to entice your couch to stay, to always live in the fountain. Your couch, however, is fond of you. It always returns before your family wakes up, to reassume its place in the living room, so no one in your house will know.
But now you know. So next time you root around in your couch's cushions for change, give the couch a look and say, "I know where these came from."
Don't forget to wink, so the couch knows its secret is safe with you.