The Slingshot Crash was a glitch in the early versions of Super Smash Bros. Ultimate. As the name implies, the glitch crashes the game when preformed. The glitch is performed by two players — one controlling Villager, and the other Isabelle. One player (either Villager or Isabelle) must do their forward or back aerial (the slingshot) and the other player has to catch the slingshot with their neutral special, Pocket. Once caught, the player currently pocketing the slingshot ball will use Pocket to toss the slingshot ball to the other player, which the other player should catch with their Pocket. Once the person who had received the slingshot ball is about to throw it, the game crashes. Weirdly, this glitch cannot be performed with two Villagers or two Isabelles.
The glitch was patched with update 2.0.0.