Unlike the usual tracks ripped on SiIvaGunner, this isn't a song at all. It's simply the voice of Charles Martinet, who was cast as Mario for the first time in a mainline Mario game, saying what would become Mario's iconic catchphrase. It's played right when you start up the game to accompany Mario's giant 3D modeled head on the title screen.
Despite not being a song, it was included on the official album Super Mario 64 Original Soundtrack[1], which resulted in it being uploaded by the real GilvaSunner to his channel alongside the rest of the album, with a unique description changing "Music" to "Text" and "Composer" to "Voice".
This voice clip was later reused for New Super Mario Bros. when re-opening the console from sleep mode.
Rips of "It's a me, Mario!" tend to have the following joke: Mario says the word "it's", and then it's followed by a different phrase that starts with the word "it's". It was ripped four times during Season 1, and twice in all seasons afterwards except Season 4/Season 4 Episode 2, where it was not ripped.