I would love a Mario game that is like the board game Clue. Imagine solving mysteries on Peach's Castle, the Comet Observatory, Delfino Plaza, etc... Every stage would have its own set of victims and suspects, for example, in Delfino Plaza, the victims would be Pianta, Noki or other islanders, and the suspects could be Petey Piranha, Gooper Blooper, and so on. On the Comet Observatory, the victims could be the Lumas or the Toad Brigade, and the suspects could be Dino Piranha, Bonefin or other Super Mario Galaxy bosses.