Unlike in ordinary chess puzzles, joke problems can involve a solution which violates the inner logic or rules of the game.
[1] Some composers have relied on real or perceived ambiguities or loopholes in the rules of chess to create humorous puzzles.
A more sophisticated example was composed by Tim Krabbé and relied on a loophole that supposedly existed in the definition of castling.
For example, direct mates and especially helpmates have been composed with the pieces in the shape of a letter or number, or even a tree.
Krabbé calls this problem the "back home task", as all eight white pieces retreat to their initial positions.
He writes that "Strategy and deep themes are absent, Black only has forced moves, but it's one of the funniest chess problems I ever saw.
The solution is: Krabbé named the "caterpillar theme" for problems and studies where doubled or tripled pawns move one after the other.
[5] The problem is "cooked" (ruined, in the lingo of chess composition), however, because 1.Kd2 also forces mate in eight moves.
In 2004, Hans Böhm sponsored a chess composing tournament for humorous endgame studies.
[8]The solution is in the words (i.e. it is a riddle): White did not lose the game of chess (which is impossible in the diagram position, as the only legal moves are 1.g7+ Qxg7+ 2.hxg7#), but rather the bet.