The Yoshi universe, sometimes known as the Yoshi's Island universe, (ヨッシー, Yoshi) refers to the Smash Bros. series' collection of characters, stages, and properties that hail from the sub-franchise of the Mario series that deals with main sub-series character Yoshi. It is generally agreed on that Yoshi and related items count as Mario properties, but Yoshi has appeared in enough of his own games alongside enough original characters and properties that many consider him as holding sway over a "sub-universe" of Mario. Yoshi is also considered part of his own universe, since the character's insignia consists of a spotted Yoshi Egg rather than the iconic image of a Super Mushroom held by other Mario characters.
Throughout the lifespan of the Famicom / NES, Shigeru Miyamoto wanted Mario to have a dinosaur companion in his games following Super Mario Bros., but apparently, limitations to the NES could not fit this companion character in. However, Miyamoto was able to achieve the debut of the character, Yoshi, in the Super Famicom/SNES launch game Super Mario World. Yoshi was designed by the game's graphics designer Shigefumi Hino (who would become famous later on as the designer of the Pikmin series), and was introduced as a species of human-sized cartoon-like dinosaurs that came in multiple different colors, could swallow enemies with their elastic tongues, could lay spotted eggs that usually hatched into power-ups, and could be ridden by Mario through levels as a mount. The Yoshi species became a permanent, recurring element in the Mario franchise forever onward, and any reference to "Yoshi" as a character typically refers to a green-colored individual that is one of the recurring heroes in Mario's world.
Yoshi, whether the character himself or the species, has appeared in a primary side role alongside various other Mario series regulars in many Mario games, oftentimes as a selectable playable character; games involving Mario where Yoshi may be selected include the Mario Kart sub-series as a recurring racer, and the Mario Party sub-series, as a recurring character choice for walking across the board and partaking in mini-games. More significantly, there have been occasional games starring Yoshi in a leading role, with or without Mario in a side role; aside from several occasional puzzle games, including Tetris Attack on the SNES, Yoshi's first high-profile starring role was in the very well-received and successful Super Mario World 2: Yoshi's Island for the SNES in 1995, several years after Yoshi's debut. In this game, Yoshi and his differently-colored friends, illustrated in a unique pastel style to help differentiate the game from the CGI imagery of Donkey Kong Country, help transport a baby version of Mario through their island's obstacles to reunite him with his brother and bring them back to the stork that is supposed to deliver them to their parents. A spiritual sequel focusing exclusively on the Yoshis, Yoshi's Story for the Nintendo 64 in March 1998, featured a more saccharine aesthetic; by this point, Yoshi had settled into a different design that gave him a more anthropomorphic appearance, which has been used ever since.
Despite the close association Yoshi's modern design has with the Yoshi's Story aesthetic, that aesthetic actually never made a reappearance in a Yoshi-centric title, whereas the pastel design style of Yoshi's Island for the SNES has been reused in several later-generation follow-ups. These may be referred to as part of the "main" Yoshi series, the "Yoshi's Island" sub-series, where Yoshi has to navigate platforming stages and attack foes with his eggs in order to transport Baby Mario and baby versions of other characters safely to the end. Aside from Yoshi Touch & Go for the DS, which appears to not even have any canonical relevance to the overall Mario franchise despite a similar scenario focused on transporting Baby Mario, there have been two direct sequels using the pastel aesthetic: Yoshi's Island DS, released for the Nintendo DS in November 2006, and Yoshi's New Island, released in 2014 on the Nintendo 3DS. Several other Yoshi games with distinct art styles have been released; Yoshi's Wooly World, released in 2015 on the Wii U with a 3DS port released in 2017 as Poochy & Yoshi's Wooly World, featured a yarn-based artstyle similar to that of Kirby's Epic Yarn, and the newest game, Yoshi's Crafted World released for the Nintendo Switch on March 29, 2019 and has a crafted aesthetic. Between these games and Yoshi's constant appearances in most Mario games, Yoshi has been enough of a recurring Nintendo character that the Super Smash Bros. series of fighting games not only included him as a regular playable character since the series' start, but saw fit to symbolically categorize Yoshi and related properties as "separate" from the Mario universe, the same way Donkey Kong and Wario have been categorized as "separate franchises" from Mario.
Ever since his debut, Yoshi became a breakout star with two major games to his name - Yoshi's Island and Yoshi's Story. Due to this, the Super Smash Bros. franchise treats Yoshi and his line of games as its own universe, separate from the Mario universe. The Yoshi universe is given almost as much representation as other franchises in Smash 64, with only one character and one stage from the universe being included. Super Smash Bros. is still the only game in the series to introduce a new Yoshi character.
The most recent Yoshi games were still Yoshi's Island and Yoshi's Story, so the content representing the franchise is still from these two games. Unique to this game, Super Mario World is counted as a Yoshi universe game. Despite having only one character, Melee features a total of three stages from the Yoshi universe, and one semi-item that only appears in an Event Match, being the Yoshi's Egg.
Full Trophy List
Main article: List of SSBM trophies (Yoshi series)
The Yoshi universe receives a decent amount of representation in Super Smash Bros. Brawl.
On the final character select screen (after all characters are unlocked), Yoshi, despite being part of the Original 8, doesn't appear in the top row in the spot between Samus and Kirby. Instead, he shares a column with fellow Mario side series characters Donkey Kong, Diddy Kong, and Wario.
Main article: List of SSBB Music (Yoshi series)
Main article: List of SSBB trophies (Yoshi's Island series)
Main article: List of stickers (Yoshi's Island series)
There is more integration between the Mario and Yoshi universes in Super Smash Bros. 4 than in previous entries. Yoshi is placed between the Mario fighters Bowser and Rosalina on the character selection screen. Several trophies of characters that debuted in Yoshi titles are categorized as Mario trophies, even though some of them were more correctly categorized as Yoshi trophies in Super Smash Bros. Brawl. In the Wii U version, numerous pieces of Mario music play on Yoshi stages and the only Trophy Box attributed to the Yoshi universe is organized between two Mario-specific Trophy Boxes. However, Yoshi remains internally recognized as an independent universe. Yoshi is still represented by his own universe logo, as are the related stages. Smash 4 features content from Yoshi's New Island - which was released between Brawl and Smash 4 - and Yoshi's Woolly World - which was released shortly after Smash 4. In the trophy gallery, the universe is internally referred to as the Yoshi's Island series.
for Nintendo 3DS
for Wii U
Main article: Enemies
Enemies that appear in both Smash Run in the 3DS version and Smash Tour in the Wii U version.
Enemies exclusive to the 3DS version. They appear in Smash Run. In addition to those listed, Mario enemies that regularly appears in Yoshi games - Koopa Troopas, Paratroopas, Lakitus, Bullet Bills, and Shy Guys - also appear. Of these, the Shy Guys behave as they do in the Yoshi's Island games. In addition to the red ones - which debuted in the Mario series - there are three variants of Shy Guy that debuted in the Yoshi series:
Main article: List of SSB4 Music (Yoshi series)
Arrangements and remixes unique to SSB4.
Arrangements and remixes from previous Smash titles. "Yoshi's Island (Melee)" has been reclassified as a Mario track.
Compositions and arrangements directly sourced from the Yoshi series with no alterations.
Main article: List of SSB4 trophies (Yoshi's Island series)
The Yoshi series receives a moderate amount of representation and received new content, such as a single new remix and some Spirits.
All Yoshi stages aside from Woolly World from previous entries return.
Main article: List of SSBU Music (Yoshi series)
Arrangements and remixes from previous Smash titles. "Athletic Theme - Super Mario World" (previously known as "Yoshi's Island (Melee)") has been classified back to a Yoshi track.
Main article: List of spirits (Yoshi series)
Games with elements appearing in the Super Smash Bros. games
Main article: Super Mario World
Technically, Super Mario World qualifies as part of the Mario universe due to it being a main series Mario game. However, the Smash Bros. games consider it part of the Yoshi universe as well, with it being Yoshi's debut appearance and one of his most iconic.