Whispy blink glitch
The Whispy blink glitch is a glitch in Super Smash Bros. Melee, first discovered by Magnus420 on SmashBoards.
The glitch only works on version 1.0.
How to perform
As Marth or Roy on Dream Land, the player must wait for Whispy Woods to blink twice. Right before Whispy's eyes are closed for the first blink, they must execute a jab, forward tilt, up tilt, down tilt, dash attack, or standing grab.
If done correctly, Marth or Roy will swing their sword in an unusual way. The attack will last as long as it normally would and the corresponding hitbox will still be attached to their arms and swords for a brief moment (except for the standing grab's hitbox which acts independent of Marth's or Roy's arm movement).
An old explanation provided by Evsen on reddit on September 2016 stated that when he was using Dolphin emulator's texture dumping feature and claimed that Marth's face was dumped on Whispy Woods. He assumed that Marth and Roy's blinking animation is tied to Whispy's, and the animation glitches because the game may have been trying to use both blinking textures at the same time. Though accepted for years, AsumSaus debunked it in 2020, who analyzed Evsen's footage and could not recreate the finding, making AsumSaus believe that Evsen might have misremembered exactly what happened.
The actual reason why the Whispy Blink Glitch occurs is because of how dynamic model parts react to the windbox created by Whispy disappearing. In this case, Marth and Roy's cape is made up of a set of 'dynamic bones' which means it sways during movement or as a result of interaction with wind effects. When Whispy's wind effect is recalled (i.e. when he blinks), the game runs a check to see if the character whose dynamic bones are being updated is Marth or Roy; if true, it runs a subsequent function which, if a series of conditions is met, tries to reload their current animation with 40 interpolation frames in an attempt to create a smooth transition between the previous and the upcoming animation. However, this operation fails to achieve its intended purpose, as the animation request reads invalid leftover data from previous calculations, making it instead apply the landing animation of Neutral Air.