The Slingshot Crash was a glitch in the early versions of Super Smash Bros. Ultimate. As the name implies, the glitch crashed the game when performed. The glitch was performed by two players — one controlling Villager, and the other Isabelle. One player (either Villager or Isabelle) needed to do their forward or back aerial (the slingshot) and the other player had to catch the slingshot with their neutral special, Pocket. Once caught, the player pocketing the slingshot ball would use Pocket to toss the slingshot ball to the other player, which the other player would catch with their Pocket. Once the person who had received the slingshot ball was about to throw it, the game would crash. For unknown reasons, this glitch could not be performed with two Villagers or two Isabelles.
The glitch was patched with update 2.0.0.