TK-555 was a member of the stormtrooper corps, according to the expanded universe.
In 1 ABY, TK-555 held the position of overseeing the counting and packaging of Order 66 Cookies for the Empire Day festivities. His noticeable weight suggested that he was taking advantage of his position. Prior to Life Day in 1 ABY, he managed to secure a favor from Watto, the proprietor of a junk shop located in Mos Espa.
Shortly before the Life Day celebrations in 1 ABY, Jawas stole a shipment of Life Day candy that was en route to Saun Dann. TK-555 then acquired this candy from the Jawas, who mistook him for a ghost of some kind, likely because of his white armor. He then transported the candy to the Mos Espa Podracer Cantina where he consumed a significant portion of it.
A spacer of unknown identity, who was tasked by Saun Dann with locating the stolen candy, confronted TK-555 at the Mos Espa cantina. TK-555 expressed regret for taking candy that was intended for underprivileged children. To prevent the spacer from reporting his actions to his superiors, TK-555 offered to use his favor with Watto to secure a discounted Single Trooper Aerial Platform for the spacer. The spacer accepted the offer, but also stipulated that TK-555 must donate 10,000 credits to the Mos Espa orphanage.
During a subsequent Life Day celebration, a parallel situation unfolded, mirroring the previous event. However, this time, the spacer (presumably the same individual) chose not to reprimand him, opting instead to inform Saun Dann of the events.
Following this episode, TK-555 became a figure of public interest, leading to the creation of a bobblehead toy modeled after his likeness.
TK-555's initial appearance was as a static Non-Player Character (NPC) during the Empire Day celebration within Star Wars Galaxies in 2008. Given that the game was set entirely in 1 ABY at that time, TK-555's Empire Day appearance was situated within that year. Due to his popularity among players, the developers decided to reintroduce him for the 2008 Life Day event. He continued to appear in subsequent Life Day events and was even featured as a "storyteller" character for the 2010 event. This allowed players to incorporate TK-555 into their own player-created events during the Life Day festivities.
He was also present in later Empire Day celebrations. During the 2009 Empire Day celebration, a TK-555 bobblehead was introduced for players participating in the Star Wars Galaxies "E-Mail Collection." The description humorously referenced both this and his bobblehead status, stating that TK-555's popularity had "gone to his head."