as you make your way through Bowser's Castle, you reach the room where you would normally fight Bowser Himself, but instead, standing there was... Luigi? wait, why is Luigi here?

he had his back turned, facing away from you "...well well well, Mario... it'sa time i quit being'a player two... so..." he spins around in a fighting stance "DID YOU'A REALLY THINK KOOPA WORKED ALO-" he suddenly realises something; you weren't Mario. "-...eh? you are'a not Mario..." (who are you?)