Back in 1996 Shigeru Miyamoto had to chose a protagonist for his first 3D platformer game. His options were either Sonic, who would swiftly save the day by defeating Bowser without making any homophobic remarks ... or Mario.

Guess which one he chose.

It's Sonic but in Mario 64. The controls at times did feel like they were too slippery even for Sonics sake, but overall it was a fun little romhack and oh my god this is the 10th time I've completed Mario 64 god help me

SM64 controls aren't the best as is, and this hack went and made them even worse. I got about 18 Stars in before deciding it wasn't worth it.

One of the most elaborate among the character mods of Super Mario 64. Sonic controls mostly like you would expect (but slides a bit too much). The problem is that the stages weren't made to go well with speed, so falling down happens all the time, specially on the most jumping accuracy demanding stages.
Underwater gameplay and camera also don't work well.
After all, it could be better, but it was a lot of fun for the most part.