The King K. Rool desync glitch, also known as Backwards Animation Glitch, was a glitch in Super Smash Bros. Ultimate that was discovered in patch 2.0.0. To perform this glitch, one player must be K. Rool, and the other character must be King Dedede. The player who is K. Rool must shoot a Kannonball towards King Dedede, who must inhale it. Then, the player playing as K. Rool must use Crownerang in the opposite direction of Dedede as the Kannonball returns back to K. Rool and hits him, launching K. Rool away. As K. Rool's crown is returning to Dedede, he must Inhale it and spit it out, and if this glitch is performed correctly, King K. Rool will essentially go crazy; his attack animations are played in reverse, and his global positioning is erratic, causing him to teleport everywhere. The glitch couldn't be removed when King K. Rool is KO'd, so the only way to stop it was by quitting the game.
This glitch is similar to another glitch in SSB4, where Bowser Jr. would have desynced animations with a specific setup.
This glitch no longer works as of patch 3.0.0.