Henlo all. It's been at least 5 quadrillion years.
Just recently while I was messing with potential kaizo(ish) tricks I could implement into a new experimental project of mine, I discovered an interesting maneuver you can do with upside down rainbow shells.
If you follow the steps below in the right order, and with the right timing:
1. Grab and hold on to the shell
2. Run left or right
3. Press and hold down
4. Quickly release the run button right after
5. Quickly spin jump after that
You end up jumping higher than your regular jump, and much higher than if you were to jump off of a rainbow shell while riding it normally, among several other things.
With this trick, Mario and Toad can clear a little over 8 blocks in height, and Luigi can clear 9. Link is unable to perform the trick for obvious reasons, and Peach seems to be unable to as well, but it seems to be because she can't jump off of a rainbow shell on her own, due to how her jump works. If anyone wants to correct me on that, please do.
I made a 1-screen level that showcases this trick (you're forced to play Luigi to prevent cheating).
Download link: Click here!
Hopefully that link works. It's a Dropbox link, so probably not.
Hope you found this as interesting as I found it to be. Off to not-even-lurking land for another several months.