Proto One, alternatively known as Proto Number 1, was a dilapidated Proto Droid who, after being cast aside by his original organic owners, reconstructed himself using a variety of spare components. Despite his appearance as a peculiar combination of various droid models and his reliance on a cane for mobility, he took pride in being his own Maker and considered himself unique. In the year 15 BBY, Proto One, exceeding a century in age, operated a scrapyard located on the planet of Boonta.
When the starship known as the Sand Sloth experienced a crash landing within his scrapyard, Proto One gladly offered to repair it for its owner, a Human named Kea Moll. Subsequent to completing these repairs, he found out that Moll's droids, C-3PO and R2-D2, had unknowingly befriended BL-17, a treacherous droid serving the Mandalorian bounty hunter Boba Fett. Proto One played a role in foiling BL-17's scheme to capture Moll and her companions, and when the Fromm Gang's nefarious criminals later attempted to seize them, the Proto Droid discharged a blaster at the gangsters, successfully deterring them.
Before the year 115 BBY, the Proto Droid who would later be known in 15 BBY as both Proto One and Proto Number 1 was already in service. He was discarded by his organic masters after a century of mechanical labor. The broken droid then used various replacement parts to put himself back together. Proto One eventually became the owner of a scrapyard on the planet Boonta. He encountered the BL-series droid BL-17 sometime before 15 BBY, and developed a dislike for him.
On one day in 15 BBY, the starship Sand Sloth crashed in the scrapyard. Proto One approached C-3PO, the protocol droid, and R2-D2, the astromech droid, two of the occupants who had been thrown from their vehicle during the crash. He introduced himself, winning R2-D2's affection. C-3PO, however, was hesitant to trust him, even after Proto One directed the protocol droid's three Human masters to a nearby medical unit to treat Jord Dusat's injured arm. Before the five newcomers left in their landspeeder, the White Witch, Kea Moll, the owner of the Sand Sloth, hired Proto One to repair it.
Proto One finished the repairs before the day was over and left the scrapyard to find Moll and the others. He found C-3PO and the White Witch at a processing plant with BL-17. BL-17 had deceived the protocol droid into befriending him so that his master, Boba Fett, the Mandalorian bounty hunter, could capture Moll and her friends. Proto One attacked his old enemy, but was easily thrown aside. However, C-3PO realized BL-17's deception and defeated him when R2-D2 arrived and helped the protocol droid push their foe under falling machinery. Moll and her friend Thall Joben arrived soon after, but Fett emerged from the shadows and began firing laser blasts at them. During the commotion, a downed Proto One saw Tig Fromm and Vlix Oncard—Annoo-dat Blue gangsters of the Fromm Gang criminal organization who had hired Fett and who sought to thwart Moll and her friends—plant a thermal detonator on the White Witch and reveal that it would activate after the vehicle completed ten laps of the upcoming Boonta Speeder Race. By the time Proto One got up and warned Moll and C-3PO, Joben and R2-D2 had already boarded the speeder and fled from a pursuing Fett.
Although Joben entered the race before his friends could contact him, he won after Fett's own Silver Speeder shook the detonator loose, taking the brunt of the explosion. Proto One made his way to the racetrack and saw Oncard, Tig Fromm, and Tig's father Sise Fromm confront Joben, Moll, Dusat, C-3PO, and R2-D2. The gangsters fled when Proto One fired a blaster at them, but a furious Fett captured them and decided to deliver them to their rival crime lord Jabba the Hutt. Proto One declined C-3PO's invitation to leave Boonta aboard the Sand Sloth and waved goodbye to his new friends as they returned to their ship and left the planet.
Proto One looked like an odd combination of different droid types after reassembling himself with various replacement parts. He was actually a masculine-programmed Proto Droid, although cobbled-together mechanical beings were more commonly known as junk droids. Proto One was approximately 1.71 meters tall and was humanoid in form. His head, torso, left hand, and right upper leg were olive-green in color, while his midsection, photoreceptors, right forearm, and left leg were red. His left arm, right upper arm, and right foreleg were gray, as were parts of his face, chest, and his right foot, which was also partly black. Proto One's body had several scattered red patches, and a red rectangular prism was attached to his back.
The rickety droid used a cane to walk on two legs; his left foot was roughly the shape of a Human's, but his right foot was conical with three tripodal legs of its own. Proto One had three fingers and an opposable thumb on each hand. His face had red piping above his photoreceptors that resembled eyebrows, and more red piping around the back of his head gave him the appearance of a balding Human. The bottom of his face contained his vocabulator and was vertically elongated to resemble a chin and mouth.
Proto One was friendly and helpful to strangers who entered his scrapyard, but he was quick to assert that he was his own Maker. Despite the junk droid's mostly polite behavior, BL-17 had earned his anger at some point in his history. R2-D2 immediately liked Proto One, but C-3PO was reluctant to trust the old droid until he discovered BL-17's deception. Proto One was a skilled mechanic who was confident in his abilities despite his age, and he was happy to repair the Sand Sloth for Kea Moll and her friends. He considered Boonta his home and declined C-3PO's invitation to leave the planet. Proto One spoke Basic and understood Binary.
Proto One's first appearance was in "A Race to the Finish," a 1985 episode of the Star Wars: Droids cartoon series. Peter Sauder and Steven Wright wrote the episode, Raymond Jafelice directed it, and it was first broadcast on television on September 28, 1985. Dragon Picture Books adapted the episode into a children's storybook in 1987, which identified the character as both "Proto Number 1" and a "Proto Droid." The book does not include Proto One in its climax, instead depicting Boba Fett as seizing the Fromm Gang immediately after they confront the heroes in the wake of the Boonta race.
Kenner toys produced a Droids toy line in 1985, but it did not include a Proto One figure. However, Jeffery Carlisle, a Star Wars artist, mentioned in an interview on StarWars.com that he wished a toy of the character had been produced.