Here is an update about everything I know about zipping in this game, as of now.
Spoilers: It's not much and I still haven't found any uses for it.
Maybe someone can eventually figure something out that's remotely useful with this.
I will use mostly youtube videos. I don't have any input files.. mostly because there really isn't much input going on.
Alright...
If you get close enough to a ceiling using the Frog, Lizard, Mole or Hermit Crab, then press select to go back to Nemo-form, the game will push you out
to the left about one tile.
If you do this while in a corner with a wall to the left and you are also holding left when you press select, you will go inside the wall and start zipping:
https://www.youtube.com/watch?v=MTOHXXzJ_yk
While inside the wall, you will zip very quickly (I don't have the exact number)
to the left. If you hold right, it will halt the zip until you let go. If you press down, nothing happens, you still zip. If you jump, even for just a frame, you will start zipping down and/or fall out of the wall/ceiling.
You can also use the staff that you have in Nightmare land, while inside the wall, but it doesn't seem to push you or make you go faster, while inside the wall. If, however, you reach the end of the wall while still holding a staff-charge, you will hover in midair until you let go:
https://www.youtube.com/watch?v=iTnJuKD1gO8
In some walls, you will start "falling" or zipping down right away, no matter what. Example: the dirt wall next to the underground key in stage 1 (this will actually take you to the secret area where the Lizard and the 1-up is).
In other wall you will go straight, until you press the jump button. Example: see the youtube clip I linked earlier.
If you zip outside the map, you die.
I've looked through the maps, tested pretty much every left-corner in the game (that you can get to with any of the animals) but still haven't found anything useful.
The closest is the spot in the youtube clip - Nightmare stage 3, right above the Bee. You can
almost make it to the platform where the mouse is, which would at least make it useful for an RTA run. But I haven't found any method to accomplish this.
You can
sometimes get pushed to the right instead:
https://www.youtube.com/watch?v=S9VuOtISN0Q
But I haven't found out exactly why this happens, or make it so that you go into a wall to the right.
Underwater, it is really easy to zip, since it's really easy to get close to a ceiling. So in stage 4 you can zip out from the cave area, right as you get out from the inner area and go around the other way instead and this is
almost faster, but ends up being a little bit slower since you lose the Frog and have to get it again.
Pressing left+right doesn't do anything special in this game, even while inside a wall. Left takes priority.
And yeah.. that's basically what I know.
Hopefully someone will find any of this useful, or get inspired and eventually find anything actually useful :)
Here is a list of thing that would definitely make zipping useful:
* Being able to zip to the right. Even for just one tile, through a wall.
* Being able to zip without going back to Nemo-form.
* Being able to zip up, or somehow gain height while inside a wall. Even just one tile would be enough.
* Being able to do a staff-boosted jump out from a wall.
Edit: I don't know if there is any difference between the English and Japanese versions, when it comes to zipping. I've played around a lot on both and haven't noticed anything, but I can't rule it out.
