Takkoman Stage 7 "Flying Spaghetti" "clip"
If you stand on the cloud it takes you inside the wall and you can just freely move inside it.
For SS Rank it's not useful, since you skip past too many enemies, it makes the route awkward.
For Any Rank it could potentially work? It would depend on what cycle the clouds are in when you get there (I don't know since I didn't look into Any Rank routing at all). Maybe if the cloud is just about to enter wall when you get there it would be faster.
I also show that the checkpoint for the boss isn't on the boss itself but on that last platform. So you can die and spawn inside boss without triggering her a first time. You can even go back all the way to start and die and you'll spawn on boss. It's not useful for anything right now, just a weird quirk.