A couple days ago I was unloading some groceries, and took my gloves off so I could better stack the yogurt. I set them on a convenient shelf in the fridge thinking, even as I set them down, "That would be a really good place to forget them. Wouldn't that be funny?" And sure enough, I promptly forgot all about them.
Troy came home an hour later and soon asked, "Is there any special reason there is a pair of gloves in the fridge?" Ha ha ha, I just started laughing, and explained how they got to be there.
It reminded me of a morning a few years ago when I got up and opened the fridge to pack my lunch and saw Troy's headlamp sitting prettily on the top shelf. Later, when I asked Troy about that, he said, "Oh I was wondering where that was." It turns out he was so tired that night that he put the headlamp "away" in the fridge. I can't remember where the glass of milk he wasn't going to finish ended up.
So if you want to have some harmless fun, pick a strange object to put in the fridge and see how your spouse reacts. (Just try not to pick objects that they might need in a hurry when they're late and trying to leave. They might not be as amused then.)