Alternate costume (SSBU)/Mii Fighter
The Mii Fighters' various costume options are distinct from how other characters' alternate costumes work, as they can be purchasable from the Shop, found behind certain Challenges, found in treasure chests in World of Light, or purchased as Downloadable content.
As it was in the previous game, while Headgear can be worn by all Mii Fighters, the Outfits are more selective.
There are a total of 134 (80 + 54) different headgear, including the 'None' headgear.
Many of the hats that were in the original game were based off of hats present in StreetPass Mii Plaza.
A total of 25 hats that were present in Super Smash Bros. 4 are absent from Ultimate.
There are a total of 144 (93 + 51) outfits, comprised of 53 (36 + 17) Brawler, 51 (29 + 22) Swordfighter, and 40 (28 + 12) Gunner outfits.
In addition to the Standard Outfits, the SSB T-Shirts were also redesigned to fit Ultimate's visual identity. All other returning outfits are largely unaltered.
The Hoodie outfit from Super Smash Bros. 4 is absent from Ultimate, as are three other Swordfighter outfits (Neon Suit, Plate Armor and Samurai Armor) and two other Gunner outfits (Fancy Suit and Mage Robe).
Mii Brawler Outfits
Mii Swordfighter Outfits
Mii Gunner Outfits
DLC costume trailers