Whispy blink glitch
The Whispy blink glitch is a glitch performed in Super Smash Bros. Melee. The glitch was first discovered by Magnus420 on SmashBoards
How to perform
The player must choose Marth or Roy in any type of Melee match or training and choose Dream Land as the stage. Then, wait until Whispy, the tree in the back of the stage, blinks. On the last 2 frames of Whispy blinking, the player must execute a jab, forward tilt, up tilt, down tilt, dash attack, or standing grab. Marth or Roy will swing their sword in a unusual way. The hitboxes for these attacks (sans standing grab) will disappear until the move finishes. This method, however, is inconsistent, and there might be other undiscovered conditions this glitch works on.
As for the standing grab, Marth or Roy does the grab without lunging forward, making it safer than a normal grab.
Explanation
No one knows why the hitbox dissappears when Whispy blinks.
One explanation provided by Evsen on reddit on September 2016 stated that when he was using Dolphin emulator's texture dumping feature when Whispy blinked. He claimed that Marth's face dumped on Whispy Wood. He asumed that Marth and Roy's blinking animation is tied to Whispy's, explaining why attack animation messes, because the game is trying to use their blinking textures at the same time. This theory was debunked after four years by AsumSaus, who asked for Evsen the footage. He played it again, he could not recreate the blinking textures again. AsumSaus stated, "...was most likely a mistake. With Evsen playing as Marth or choosing Marth as the second character, seeing Marth's blinking textures being dumped and later misremembering."
To this day, the reason behind this glitch is still unknown.