An idea that has been in my head for a couple of years; a Pokémon game setting in a Mario World, and Isle Delfino is the perfect place to do so. The idea is that you battle enemies from the game itself and meet the characters and visit the places from the game too. The 'only' difference is that the whole gameplay is different, instead of jumping on enemies' heads in real-time battles, you use PokéBalls to capture Mario enemies in Pokémon Battles, fight against other inhabitants, battle through gyms etc. In short, a Pokémon game with the characters from Mario.
This is just the map of what the island would look like.
No, I'm not making a game, I don't have the skills nor the time to do so. I'm not even sure if there will be more of this; the cities and maps themselves etc.