The Yoshi universe 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 because his smasher's insignia consists of a spotted Yoshi Egg rather than the iconic image of a Super Mushroom held by other Mario characters.
 Franchise description
Throughout the lifepsan 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 specie 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 specie, 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 subseries, as a recurring racer, and the Mario Party subseries, as a recurring character choice for walking across the board and partaking in minigames. 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 bring him back to the stork that is supposed to deliver him to his 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" subseries, 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 the most recent Yoshi game, Yoshi's New Island, slated for a 2014 release on the Nintendo 3DS. 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.
 In Super Smash Bros
If treated separately from the Mario universe, the Yoshi universe is only about as big as most of the other franchises represented in SSB, with one character and one stage represented, and there is no item that can be considered Yoshi-centric.
The character, Yoshi, is considered both part of his own universe and part of the "Marioverse."
If the Yoshi universe is counted as separate from the rest of the Mario universe, Super Smash Bros. features one Yoshi-themed stage:
 In Super Smash Bros. Melee
While Melee is much bigger than Smash, none of the game's items are based on Yoshi save for the Yoshi's Egg item which was only used in an Event Match, There is only one character, two new stages along with Yoshi's Island returning from the previous game, and a bunch of new Trophies.
 Common Enemy
 Full Trophy List
 In Super Smash Bros. Brawl
The Yoshi universe receives 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 (probably because Yoshi is the only character representing his franchise). Instead, he shares a column with fellow Mario side series characters Donkey Kong, Diddy Kong, and Wario.
 Common Ally
 Common Enemies
 Games with elements in Smash Bros. games
 Super Mario World
Technically, this game falls under the Mario universe category, but there are several elements from the game that goes with movesets and stages.
In Super Smash Bros. Melee, there is a stage called Yoshi's Island that is based off of that game. A few of Yoshi's moves in all three Smash games are also based off of what he could do in that game. In Super Smash Bros. Brawl, Yoshi's Final Smash, Super Dragon, is based off the fact that when Yoshi eats certain kinds of Koopas, he gains some kind of ability, such as being able to breathe fire with a red Koopa.
 Super Mario World 2: Yoshi's Island
In Brawl, there is a stage called Yoshi's Island that is based on many elements from that game, such as the design of the stage (which looks similar to drawings) and the background characters. There are also some pieces of music that come from the same game. They all play on this stage.
Some of Yoshi's special moves come from this game.
 Yoshi's Story
In Super Smash Bros., there is a stage called Yoshi's Island that was based on this game, featuring the Super Happy Tree and other characters from Yoshi's Story in the background, and a main platform resembling an opened book. This stage returned as a past stage in Melee.
In Melee, there is another stage based on Yoshi's Story, which is also named after it.
A remix of the game's closing music is included in Brawl and plays on the new Yoshi's Island stage, which is based more on the Yoshi's Island franchise than Yoshi's Story.
 Other Games
Other games such as Yoshi Touch & Go and Yoshi Topsy-Turvy have their songs and stickers in Brawl.