Earlier this year as part of the Super Smash Bros. Ultimate fifth anniversary celebrations, Nintendo added brand new spirits to the game. This included all sorts of franchises and one of the highlights was the Pokémon Scarlet and Violet spirit collection.
If you didn't manage to get them back in February, the good news is they've now been made permanently available on the Spirit Board and also via the in-game shops. Thanks to Serebii.net for the heads up about this.
Some other spirits that joined Smash Bros. for its fifth anniversary event were based on series like The Legend of Zelda, Xenoblade Chronicles, Splatoon and even Pikmin. A bunch of third-party spirits were also added to the game covering games like Hades and the Atlus hit, 13 Sentinels: Aegis Rim.
Development on Ultimate officially wrapped following the release of the Sora (Kingdom Hearts) amiibo earlier this year alongside the final major update for the game, which bumped it up to Version 13.0.2.