Luigi... He's always been Mario's second banana, the "Player 2", the one who doesn't get the Princess in these early games. No matter how identical he is to Mario in skillset and ability and tenaciousness and bravery, at the end of the day the game is "Super Mario Brothers", and he's just "the Brother".

How he must've hated Mario... Who among us wouldn't? Think about it. No matter what happens, Mario always comes back. No matter how many corpses he leaves littering the battlefield, he's always there once more to leap and cheer and get all the adoration.

And Koopa hadn't worked alone? I didn't know what that meant at first, if anything, but again you just have to think it through. HOW exactly does King Koopa consistently succeed in kidnapping the Princess?

From day one, from the original Mario Brothers onward, it had always been an inside job.