what it is: simply a glitch. Even TASers do not fully understand why this happens and it simply can not be explained with any previous logic we have learned from the game. I read somewhere that the teleport lasts as long as the character's Pre-Jump animation. IIRC, jiggly is in this state longer before she jumps and therefore has a longer and more drastic teleport than samus and fox (what I dont understand is if its simply the pre jump animation, why cant all characters do it?)
how to do it:
1. Be in a full run (not initial dash) with either jiggs fox or samus.
2. Mash the control stick in the opposite direction as you are running
3. Jump 3 frames later.
The close you get to 3 frames, the more drastic the teleport looks. jumping on frames 2 and 4 get a smaller teleport.
You can either
(A) cancel the teleport with a usmash which looks like this
http://www.youtube.com/watch?v=bdggE9_qbiI
(B) Cancel the teleport with UPB, which is a terrible idea with fox or samus. With jiggs it can produce a gigantic slide if canceled with sing.
http://www.youtube.com/watch?v=4gH4z7gRpLY&feature=related
(C) Just use the jump and do an arial.
http://www.youtube.com/watch?v=FCkRtKck30U&feature=related
If done close to the edge, it will actually slide off without doing a jump