UPDATE 20/9/17: Nintendo has taken down the videos of Super Mario 64 Online posted on its creator's Patreon and YouTube.
According to the romhack's creator, Kaze Emanuar, Nintendo removed 20 of his videos videos, closed down his Patreon and filed a DMCA complaint about two of his discord uploads.
When you try to watch any of the videos, a message appears saying, "this video contains content from Nintendo, who has blocked it on copyright grounds".
ORIGINAL STORY 11/9/17: You can now play Super Mario 64 online with up to 24 people thanks to a new fan-made project called SM64.
The SM64 romhack is the brainchild of Kaze Emanuar, Melonspeedruns and Marshivolt. It allows players to connect online, pick their character from a line-up which includes the usual suspects such as Peach, Wario, Mario and Toad, and cause chaos as a group by brawling, playing hide and seek, racing or just playing the game the way it's meant to be played - but where's the fun in that?
You can check out the trailer for the project below (details on how to download are in the description). If you are having trouble there is also a tutorial video on how to download the mod.
The original Super Mario 64 was released in 1996 for the Nintendo 64. SM64 is built on a Super Mario 64 ROM for PC and seems to have all the heart and soul of the beloved original.