WarioWare Inc., or Made In Wario as it's called in Japan, is a game developed by Nintendo for the GBA. It is also one of the most insane Japanese games I've played for a long time, plus it has a highly innovative structure.
The backstory of the game, weird and kooky as it is, involves lovable rogue Wario wanting to become rich by developing games (ho-hum). It's all an excuse for presenting you with 200 mini-games, which all last about four seconds. That's right. Four. The objective of each sub-game is to figure out what the rules are, and then win it. The games recapitulate action genres, other Nintendo games, classic games, but sometimes are just plain weird in a Bishi Bashi kind of way (another classic). The presentation is between the games is lightning-fast and bizarre beyond words. I love it.
It sounds totally weird and counter-intuitive, but it's a ton of fun. Additionally, it must have been fairly easy and cheap to develop. It's a gimmick that's hard to apply in a general way, but who wouldn't want to have a fun, addictive and hard-to-imitate game based on a top franchise?