Is it a puzzle or is it a magic trick? Impossible objects are difficult to classify. They really aren’t mechanical because they don’t move (usually) and you don’t manipulate any of their parts to solve them. You just look at them and think. And they aren’t really a magic trick. There’s no performer, at least not when you’re dealing with the object. But they have the same “how did they do that” quality that a magic trick has. The puzzle is to figure out how they were made.
Neat things to look at. I have no idea how they’re made.