SLAPAYO
Naruto[NU] fist discovered the glitch on March 30th, 2008. However, on May 4, 2008, the SLAPAHO crew provided the first documented evidence of the creation of the glitch.
The details of the glitch are still uncertain, and there are many questions after reviewing the video. The SLAPAHO crew is currently running tests to discover how the glitch works and what it does. Unfortunately, in their haste to have video evidence of the glitch, the crew quickly ended the match with little experience of the glitch itself so the replay could be saved.
What is known is that it involves Ness being hit when his yo-yo is outstretched at a particular point during his up smash, and causes the yo-yo to fail in retraction, effectively leaving the yo-yo limp at Ness' side. The yo-yo appears to retain its hitbox, but will only hit an opponent or damageable object once, very similar to the function of the SLAPASTICK.
More research will be conducted to discover all facets of the glitch.
Melee
A similar glitch occurs in Melee with Dr. Mario reflecting a poke ball to Mario, where Mario's cape "breaks" and his cape hangs out the entire time.
Video
SLAPAHO's Video:
<youtube>Hl4cUSg53DU</youtube>
Naruto[NU]'s Video:
<youtube>dVAB8wgaaHw</youtube>