Super Mario 64 DS - Supersliding

This glitch allows you to superslide, with your speed value locked. It's only possible in the castle and castle grounds, because it requires a rabbit.

I'll start by explaining the effects of this glitch. There are two variants to this: if you have 1 or 2 health the more interesting variant occurs, and with any other amount of health (apart from 0 obviously) you get the other one.
The way the version requiring 3-8 health works is that you will slide infinitely in one direction with your speed locked. You can't jump, eat, etc, all you can do is turn the camera. This superslide can be stopped if you slide into water, onto a steep slope, or take damage so you are at 1 or 2 health (triggering the other variant). You can also delay the superslide using neutral jumps. If you fall off a ledge then the game will still treat you as being on the ground. You can also go through doors if you slide into them while facing them.

The version of this glitch that occurs when you have 1 or 2 health is a lot less restrictive. You can turn, for a start. You can also jump, long jump, slidekick, etc, but only when not holding a direction. However, holding no direction for a couple of seconds will cause your superslide to function in the same way as the first version.
The effect of being treated as on ground while in the air also applies for this version, and can be abused. By releasing a direction while in mid-air you can perform a frame-perfect jump. Another cool effect is that you can't go into first-person while supersliding. This means that by pressing X and then going off a ledge, you can activate first-person mode in mid-air. It is automatically cancelled, but you not before setting Yoshi's Y velocity to 0. You can then hold a direction to start supersliding in mid-air with 0 speed, press X twice, and release the direction again, to continually set your Y velocity to 0 and slow the rate of your fall dramatically by repeating this. I show this off at 1:01.

Both versions of the glitch can be cancelled using a reset, dying, or entering a loading zone. Until then Yoshi will always start a superlside when on solid ground.
When supersliding forwards, Yoshi's speed is capped at 131040 (his max running speed). When supersliding backwards it is capped at -57344.


Now for how the glitch is actually brought about... some stuff will need to be explained for this to make sense.
There are 3 methods to do this, all found on quick succession. Another very related glitch I discovered today is what makes methods 2 and 3 possible: if you have 1 or 2 health, then you can move after eating a rabbit. You see, the reason supersliding works is that you're abusing the mechanic put in to keep you at 0 speed after catching a rabbit: it only locks your speed and doesn't set it to 0. So every time you catch a rabbit you are doing a superslide with a speed of 0, in a way. This means that by having 1 or 2 health when you catch a rabbit, the variant of a superslide that allows you to jump occurs, and you can move.
Additionally, it is possible to move after eating a rabbit with any health, by catching it on a steep slope, which will start you sliding.
And lastly, you can eat a rabbit and jump at the same time to keep it in your mouth, similar to the Star Cancel Glitch, which means you can spit it out anywhere. This means you can position yourself next to a steep slope or something else useful before spitting it out.

Method 1: This is the method shown in the video. Catch a rabbit, and then enter water through either having 1 or 2 health, by catching the rabbit on a steep slope, or carrying it to  a steep slope then spitting it out. After collecting the key while in water, select either Save and continue or Save and play mini-games. Pause right as the selection textbox closes and now unpause. This will skip saving and keep Yoshi in the state he's in while the key travels to him, where his speed is locked and he can superslide.

Method 2: Start by having 1 or 2 health. Catch a rabbit within the castle, and then run to anything that brings up text: a sign, Toad or already caught rabbit will work. On the frame that you collect the key press A or B to interact with the object, and the key will never be properly collected, like with the original Phantom Key Glitch (Super Mario 64 DS - Phantom Key Glitch). You can do this with 3-8 health, but you are essentially softlocked as you are stuck with 0 speed.

Method 3: Start by having 1 or 2 health. Catch a rabbit within the castle and then go through a door. You can now superslide, but the key will try and get to you again if you go back to the room you caught the rabbit in.

Method 3.5: Go through the door the same frame you collect the key. This will stop the key from ever being properly collected, and you don't have to worry about it.