https://www.polygon.com/2018/12/18/18146384/super-smash-bros-ultimate-isabelle-glitch-assist-trophies-waluigi

In case you remained unconvinced that Animal Crossing’s Isabelle is one of the greatest additions to the Super Smash Bros. canon, players have found an amazing bug that only works when the perfect Shih Tzu is the sole combatant in a match. See, when at least two Isabelles get together, beautiful chaos happens.

And all they need is a fishing rod and an Assist Trophy.