That drive us crazy and our RADs know this. Certainly it's a rare child indeed that doesn't do something to drive his/her parents up the wall at least on occasion, but I think our RADs take it to a whole new level.
Due to our RADs food issues along with her diabetes, we keep pretty much everything with carbohydrates locked up in our bedroom closet. The only items we can't do that with are, obviously, the things that need to be refrigerated. This includes juice, which is to a diabetic, what spinach is to Popeye - it's essentially super glucose reserved for low blood sugars. When wife and ODD were off camping for the week I didn't have any problems with leaving both orange juice (which she doesn't particularly care for) and apple juice (which she loves) in the fridge. All week long it went untouched.
Enter wife and ODD. They returned home late Saturday night after RAD had gone to bed. One of the things they brought back with them was a small unopened single-serving bottle of apple juice which was put in the fridge. Note the word "unopened".
The next morning as we were preparing lunches for a day out, we were gathering the drinks when the wife pulled out the small bottle of apple juice and it started leaking. That's when we noticed it had been opened and a medium sized sip had been taken. Not a small sip, not a glug or a chug, but just enough of a sip to make it obvious *somebody* had some (as if the broken seal wasn't enough of a clue). ODD denies doing it (she would have likely drank the whole thing), RAD denies doing it, and the dogs don't have oppose-able thumbs so I'm pretty sure they weren't behind it.
A little thing? Yes, but also a big thing. Whoever did it, knew it would be found, knew what kind of chaos it would cause, and obviously did it intentionally. If it were an isolated incident it wouldn't really be a problem. But it is just one of many small things that happen with great regularity and seem designed to drive us crazy. Or, I shouldn't say "us" since a majority of the things that mysteriously happen are specifically targeted at the wife or ODD. It's never my stuff - always theirs. It's rarely something that I would notice, but almost always something that is blatantly obvious to them. Is it ODD trying to get RAD into trouble? Is it the wife really going crazy? Is it RAD acting out her issues with family, and women in general? Is it evil monkeys sneaking into the house at night to have fun? I don't think we'll ever be able to prove it one way or another....