He’s Mario. He’s got the same cheerful-yet-serious personality and mannerisms, he’s got the same voice and accent, but he’s in 64 bits. This was Mario back when he had to restore the power of the Power Stars (which were hidden in magical paintings by Bowser) to the castle in order to save Peach. He knows the entirety of Peach’s Castle, like the “endless” stairs (and the BLJ) and what’s inside the paintings. He recognizes everything he encountered in Super Mario 64.