The yo-yo stack glitch is a glitch in Super Smash Bros. Melee that results in Ness having several of his down smash yo-yos visible at once. By using a down smash on the earliest interruptible frame of a previous down smash (frame 59), the old yo-yo is retained instead of disappearing, following one frame behind the new yo-yo. The process can be repeated indefinitely to stack further yo-yos, resulting in a kaleidoscoping effect due to the intersecting polygons. Interrupting the down smash on a slightly later frame, or interrupting with an up smash instead, will keep the current number of duplicated yo-yos but not add another. The glitch ends naturally once the chain of interrupted up or down smashes does, and it has no effect on the move's hitboxes.
The glitch was discovered by Mofo during the DDoS attack on Smashboards in 2013.
