Alternate costume (SSBU)
Each character in Super Smash Bros. Ultimate has a set of alternate costumes that feature different colors or designs. Due to the presence of 8-Player Smash, all characters have eight costumes except for the 3 Mii Fighters, which have a variety of costume options.
Some characters possess certain alternate costumes with more drastic design differences, and are not merely recolors of their standard outfits. Mario, Piranha Plant, Wario, Link, Zero Suit Samus, Ridley, Ike, Isabelle, Little Mac, Shulk, Cloud, Bayonetta, Joker, Sephiroth, and Kazuya have different outfits available; Hero’s costumes represent different protagonists across the Dragon Quest series; Pikachu, Pokémon Trainer, Villager, Wii Fit Trainer, Robin, Corrin, Inkling, and Byleth all have male and female variants; and Olimar, Bowser Jr., and Steve have model swaps that change them into different characters with different names, complete with corresponding voice and Announcer clips, though like all other alternate costumes, they bear no gameplay differences.
Half of Bayonetta's costumes are based on her design from Bayonetta 2, while the other half are based on her design from Bayonetta. For the former half, she wields Love is Blue, which has blue attack trails. For the latter half, she wields Scarborough Fair, which has red attack trails, and speaks English even in the Japanese version. Her Bullet Climax has slightly different sound effects for the two different costume types.
Instead of alternate color schemes, Bowser Jr.'s alternate costumes consist of the Koopalings. Bowser Jr.'s Junior Clown Car is the only one with black eyes and horizontal orange "eye paint", while the Koopalings' mass-produced Clown Cars have yellow mechanical eyes with vertical black "eye paint". Aside from Roy and Morton, whose positions are swapped, the Koopalings are listed by the order they are fought in Super Mario Bros. 3.
Half of Cloud's costumes are based on his appearance in Final Fantasy VII, while the other half are based on his "Cloudy Wolf" design from Final Fantasy VII: Advent Children. In two of his Advent Childen costumes, his Geostigma-infected arm is covered by a sleeve, while it is exposed in the other two, revealing the red ribbon he wrapped around it in memory of Aerith Gainsborough. His costumes with the exposed arm are based on his appearance in Advent Children after his fight with Bahamut SIN, during which his sleeve is torn off. As of Sephiroth's official release, Advent Children Cloud uses Omnislash Ver. 5 as his Final Smash rather than the standard Omnislash, which is mostly a cosmetic difference; however, the explosion resulting from the move's final hit has slightly different properties regarding the direction in which it launches enemies who were not caught by the rest of the move, thus technically making Cloud the only character in the game with a gameplay difference between his costumes. Cloud’s alternate costumes are slightly brighter compared to Smash 4.
Half of Corrin's costumes are male, while the other half are female.
Half of the Hero’s alternate costumes represent different protagonists from across the franchise. The other half are recolors of the first four.
The Ice Climbers switch positions and the player controls Nana when using the red, brown, white and orange costumes. The stock icons and character select portraits change to reflect this.
Ike uses his Ranger design from Fire Emblem: Path of Radiance for half of his costumes, and his Hero design from Fire Emblem: Radiant Dawn for the other half. Each design was previously used for his appearance in Brawl and Smash 4, respectively.
Inkling alternates between the female and male versions from the original Splatoon. Aside from the first and fifth costume, the costume colors match the respective port color.
Half of Isabelle's costumes are based on her Summer Outfit, and the other half are based on her Winter Outfit.
Two of Joker's alternate costumes place him in his Shujin Academy uniform from Persona 5. When wearing his school uniform, Joker takes off his glasses when summoning Arsène instead of his mask.
Half of Kazuya's costumes are based on his signature style of a flame embroidered Gi bottom with no top, and the other half are based off his alternate trenchcoat suit outfit from Tekken 7.
Main article: Alternate costume (SSBU)/Mii Fighter
The Mii Fighters' various costume options are distinct from how other characters' alternate costumes work. Unlike in SSB4, the colors of Mii Fighters' outfits are now customizable.
Min Min's first four costumes are based upon the color schemes that could be selected by clicking, holding, then tilting the control stick in ARMS.
Pac-Man's stock icons are the only ones that do not alter its colors directly to represent each palette swap; instead, a colored neon bar (appearing similar to the wall sections from the original Pac-Man) is used under the stock icon. Most of his alternate costumes change his model to give him colored armbands and/or the Wing Shoes power-up from Pac-Land.
For each costume, the container Piranha Plant sits in alternates between a pot and a pipe.
Only the starting Pokémon is shown on the character selection screen; it can be changed by hovering the cursor over it and selecting it. All of Pokémon Trainer's alternate costumes reference a protagonist from each generation of the Pokémon games. The colors below correspond to Squirtle's shell, Ivysaur's bud and Charizard's skin.
R.O.B.'s default costume switches between the first and second ones listed depending on the game's language.
Half of Robin's costumes are male, while the other half are female.
With the exception of the purple costume, Rosalina's costumes are complementary to Peach's and transitively may share some sources of inspiration. Additionally, while not traditional alternate costumes, there are six different-colored Lumas outlined here.
Sephiroth's base design for Ultimate is based on his redesign from Final Fantasy VII: Advent Children with some design elements taken from his in-game model from the original Final Fantasy VII such as the brown-colored straps on his shoulder guards, while his Coatless design is from the final cinematic boss fight in the original Final Fantasy VII. The design of his sword the Masamune is based on the Final Fantasy VII: Advent Children variant with the blue leather wraps with a golden hilt, and a golden handle guard with loops on two of the four sides. His wing, which debuted in international versions of the first Kingdom Hearts game, uses its design from Final Fantasy VII: Advent Children.
With the exception of his first and last alternate costumes, all of Shulk's alternate costumes are based on the color schemes of his party members from Xenoblade Chronicles. His hair now also changes colors to match these characters.
Three of Steve's alternate costumes replace him with Alex, one replaces him with a Zombie, and one replaces him with an Enderman.
Terry's palettes are based on designs from his own games, and the design on his cap changes for each one.
Villager's appearance varies greatly between costumes, with differing eyes, hair, gender, clothing, and skin color. All of Villager's alternate costumes, with the exception of the yellow costume, are based on how the player may look at the start of a new game depending on how they answer questions asked by Kapp'n or Rover in Animal Crossing: Wild World and Animal Crossing: City Folk, respectively.
Wario alternates between wearing his biker outfit from WarioWare and his overalls from the Mario and Wario Land games.
Wii Fit Trainer alternates between the female trainer and the male trainer. Both of them are characters from the original Wii Fit.