Ive been trying to do the cloud glitch, and there is lots of guides on how to do everything, but what is fast yoshi? how do I do it?

Fast yoshi is if you hit the yoshi block twice on the same frame. The easiest way to do this is to throw a shell up and jump up so the shell and Mario hit it on the same frame. Fast yoshi isn't necessary for cloud though, it just halves the time yoshi takes to hatch.

(It happens because hitting the block twice spawns two yoshis and the hatching animation is shared between them; spawning three yoshis would make them spawn 3 times as fast etc. Not that you need to know this bit )

oooh thank you

you're welcome

MajicalPony: What's fast yoshi Jumpyluff: ¤insert yoshi here¤

Yup, that's what happened