The idea of having an avatar for the player in the Fire Emblem series was previously explored in Fire Emblem: The Blazing Blade on the Game Boy Advance and Fire Emblem: New Mystery of the Emblem on the Nintendo DS. These two games featured avatar characters named (by default) Mark and Kris, respectively. Mark, however, is not a playable unit, nor is he a pivotal character in the story; his appearance is often hidden and thus his customization is limited to gender, name, and birth month (blood type in the Japanese version). It was not until the creation of Kris when an avatar character could be used as a unit on the battlefield, and would be given prominence and personality in the story on par with its main character, Marth. Kris' customization is also greatly expanded from Mark's, giving the player more freedom for their appearance and playstyle.
Fire Emblem Awakening reuses the idea of an avatar character through a customizable character named Robin by default, who is a main character alongside Chrom, similar to Kris and Marth before them. This idea was later used in Fire Emblem Fates, with Corrin.
Before the story begins in earnest, the player is met with a Premonition, which briefly highlights the events of an alternate timeline. In the beginning of the game, Robin is found lying in an open field by Chrom, his sister Lissa, and his bodyguard Frederick. They find out that Robin is an amnesiac who remembers nothing besides their name, Chrom's name, and his incredible knowledge and experience in fighting battles, which Chrom experiences firsthand after they manage to save a small settlement from a larger group of brigands. Frederick suspects Robin of being a spy due to remembering Chrom's name before their own, but Chrom is convinced of Robin's good intentions and invites them to join the Shepherds as their chief tactician, with the two quickly becoming close friends. Ylisse, Chrom's home country, is then faced with a war against Plegia (which is later revealed to be Robin's home country) and another against Valm two years later, both in which Robin's tactical expertise proves very helpful, especially given Ylisse's limited number of soldiers. There is also the constant threat of the Risen, undead soldiers who terrorize parts of the continent of Ylisse. As the Shepherds continue to fight and recruit more capable members, Lucina, Chrom's daughter from the future, properly introduces herself to them, having only met them while she was disguising herself as Marth. She, alongside the children of other members of the Shepherds, travelled back in time to warn them about the revival of the Fell Dragon Grima after her own world was put on the brink of destruction courtesy of him. Robin, Chrom, Lucina, and the rest of the Shepherds make it their new mission to prevent the Grima of the current timeline from surfacing.
In game, Robin starts in the Tactician class. This class is exclusive to Robin, their children, and DLC characters, and enables them to attack with magic tomes as well as swords. As the avatar character, Robin and their children can switch to any starting class the player desires using a Second Seal (aside from Lord, which is exclusive to Chrom and Lucina), making for one of the biggest skill pools possible for a single character. Robin can also support with every other character (as Kris could previously), and marry any opposite gendered character the player wants, including the future children of other Shepherds that are met via Paralogues (side stories) as more characters within the Shepherds marry each other. Robin's customization focuses more on appearance and even features several options for voice.
Since Awakening, Robin has also appeared as a guest character in Code Name: S.T.E.A.M., Fire Emblem Fates, and Fire Emblem Echoes: Shadows of Valentia, in each case summoned in-game using his amiibo. Appropriately, these games and amiibos also use the same "default" version of the male avatar depicted in Smash. The crossover games Fire Emblem Heroes and Fire Emblem Warriors feature both the default male and female versions of Robin as playable units.
As a playable character
Main article: Robin (SSB4)
Robin appears as a newcomer in Super Smash Bros. 4. Players can choose either the male or female models of the character, based on the default appearances for both genders in the Tactician class. They use tomes of various elements (Fire, Thunder, Wind, and Darkness) along with a Levin Sword. Their tomes and Levin Sword have a limited amount of uses before they break, reminiscent of the durability system in the Fire Emblem series; they will recharge after a certain amount of time has passed. If the Levin Sword breaks, they use an unbreakable Bronze Sword instead.
On the current tier list, Robin places 37th out of 55, at the bottom of D tier (tied with Samus). The various tomes at Robin's disposal allow for a strong zoning game, which also grant versatility for use in many different situations. The Levin Sword is also quite powerful, possessing generally high knockback, especially with up aerial. Although the durability system implemented into the tomes and Levin Sword temporarily disable some of Robin's attacks, the sword and tomes themselves can be picked up before they disappear and used as strong projectiles. However, Robin's main weakness is poor mobility, having the slowest running speed out of all fighters. They also have mediocre defensive games, which combined with their poor speed, can leave them open to assaults at close range, especially by fast characters. Overall, Robin has garnered some notable players, though only has average tournament results.
As a playable character
Main article: Robin (SSBU)
Both the male and female Robins return as playable characters in Super Smash Bros. Ultimate. Unlike Smash 4, Robin is an unlockable character rather than a starter character.