Yo-yo glitch

Ness taunting alongside the disconnected yoyo hitbox.

The yoyo glitch refers to a glitch done using Ness's yoyo. It can be used to attack or grab with near limitless range or attach certain single-hitbox attacks to Ness's body. The discovery of the glitch was a collaborative effort between VilNess, LonelyNess, and Dan Smith, and was spurred on by an innocuous video of an unknown Japanese player accidentally dropping a yoyo hitbox.

In Melee, the glitch can be performed in all versions of the game.

Mechanics

Ness's up smash consists of 3 parts each with its own hitbox: outreaching, spinning, and swinging. The yoyo glitch drops the last hitbox of the up smash onto the ground and leaves it there until Ness gets KOed or uses a non-projectile attack.

How to perform it

Use Ness's up smash and hit any opponent or destructible part of the stage with the outreaching part of the yoyo. Charge the yoyo very slightly before releasing.
Make sure that, after the yoyo is released into its upward swing, it doesn't hit anything else.

Follow-up techniques

Thunder jacket

A follow-up technique to the yoyo glitch discovered by Simna ibn Sind.

Instructions:

Perform the yoyo glitch.
Use PK Thunder to floorblast Ness from the air or use PK Thunder to hit Ness into a ledge and grab it.

Effects:

Attaches the hitbox of PK Thunder 2 (Ness's recovery attack) to Ness's body.
Blocks most attacks that it collides with and hurts opponents and destructible stages.

Spike jacket

A follow-up technique to the yoyo glitch discovered by MasterofFlames.

Instructions:

Perform the yoyo glitch.
Use the down aerial and land immediately after the hitbox comes out. This can be done by SHFFLing.

Effects:

Attaches the hitbox of Ness's down aerial to his lower body.
Meteor smashes opponents and hurts destructible stages.

Star jacket

A follow-up technique to the yoyo glitch discovered by MasterofFlames.

Instructions:

Perform the yoyo glitch.
Use the up aerial and land immediately after the hitbox comes out. This can be done by DjCffling.

Effects:

Attaches the hitbox of Ness's up aerial to his upper body.
Pops up opponents and hurts destructible stages.

Toy jacket

A follow-up technique to the yoyo glitch discovered by Earthbound360.

Instructions:

Perform the yoyo glitch.
Use the up smash or down smash on a disappearing platform timed so the platform disappears right as the yoyo comes out. This can be done on the awnings in Onett.

Effects:

Attaches hitbox of Ness's up smash or down smash to his feet.
Causes either weak or strong yoyo knockback based on the timing of the setup.

Deadline

A follow-up technique to the yoyo glitch discovered by LonelyNess.

Instructions:

Perform the yoyo glitch.
Use any non-projectile attack or a grab and that attack will hit every target in between Ness and the location the yoyo glitch was perfomed (if a grab is used then only the target closest to Ness will be affected).

Effects:

Adds near-limitless range to Ness's attacks.

Super Yoyo Glitch

It is a very rare occurrence, so very little about it is known. Its effects (including but not limited to infinite Jackets and instant KO throws) are similar to those of the Yoyo Glitch, but are more lethal and have longer lasting effects.

This technique holds much value to Ness players and is said to be the secret to beating the Bowser Challenge.

Gallery

Ness performs the first step, creating a trap with a dropped hitbox.
If the enemy is in between Ness and the dropped hitbox, all of his A attacks, grabs, and PK Thunder 2 will hit the opponent.
Not only can you grab the enemy, but smash attacks work too.
Using the deadline to smash from long range, with hitboxes visible.
Deadline even works with PK Thunder 2, the attack that occurs when Ness hits himself with pk thunder.
Ness runs into Samus while wearing a Thunder Jacket
The glitch is viable for tournament use: here, Mofo performs the glitch and grabs Hax (Captain Falcon) from long range.
In the same match, Mofo installs a Thunder Jacket. He is hit by Hax, who is KO'd by the jacket. Mofo is hit by the tail of his PK Thunder and survives.
Toasty turns the hitbox into a down aerial hitbox, and then charges his PK Flash. The down air hitbox pops Link into the air, where he is hit by the PK Flash.