Gemischtes Doppel is an unusual German Memory-type game where the cards in a pair may look very different: matching cards are connected through spoonerisms. Each card in a pair shows a word that is a similar-sounding anagram of the other card's word, each accompanied by its own illustration.
Here is an example of two cards that form a pair: Gartenkunst - Kartengunst. An English version of the game might have you hunting for a Bad Salad to match the Sad Ballad you just found.
The format originates in "the world's shortest column" (two words ... plus two pictures) from the weekly Süddeutsche Zeitung Magazin. The juxtaposition of incongruous concepts, the odd but perfectly understandable expressions for familiar concepts that often result on at least one side of the anagram, and the deadpan stock photography illustrations are all played for absurd humour.
This sort of memory based on playing with words is more difficult than the usual one. The funny images displaying these words add to the fun.