Hmm .. it's pretty tough to claim I invented any dishes. I don't own any recipe books, but I cook everything from Beef Stroganoff to Lasagne by guessing the ingredients and methods.
The most interesting thing I've made though was a form of takoyaki I like to call 'Nandemoyaki'. Takoyaki are little savoury dough dumplings with a piece of octopus inside - very popular in Osaka. With Nandemoyaki, I just grab random ingredients from my fridge and cupboard and mix up fillings.
The best was probably the Bacon, Kimchi & Bean Sprouts Nandemoyaki.
As a side note - a fun game we used to play in a local bar in Osaka was 'Russian Roulette' using takoyaki. You'd have six takoyaki - one of them was filled with fresh wasabi instead of any octopus. You and five mates would all grab one and eat at the same time, carefully watching each other, trying to guess who had the one that was entirely wasabi.
Me, being me, would order this for myself and eat all 6.