Ultra Boy (Jo Nah of the planet Rimbor) is a fictional character, a comic book superhero in DC Comics. He is a member of the Legion of Super-Heroes in the 30th and 31st centuries of the DC Universe. He has the powers of superhuman strength, flight, penetra-vision (similar to Superboy's x-ray vision, except penetra-vision allows him to see through lead), flash vision (similar to heat vision), invulnerability, and ultra-speed. All of these abilities seem to be at Kryptonian power levels, but he can only use one at a time. Because of this he cannot use his ultra speed to break the "time barrier" since the stress would destroy his non-invulnerable body. With his Legion flight ring (or earlier flight belt) he can use another power while flying. Like all Legionnaires, he can use a transparent space suit allowing him to survive in space.
Ultra Boy gained these powers when the space-speedster he was flying was swallowed by an ultra-energy beast (a "space whale"), exposing him to radiation while inside. His real name is derived from the biblical figure Jonah who also survived being swallowed by a "large fish" (often considered to be a whale).
Ultra Boy's costume features an emblem some believe represents the beast on his chest. It has no cape, yet originally was the busiest of all the Legionnaires' costumes, with a red top that had black striped cuffs and the aforementioned emblem in light green, a light green weight belt with three slots, black shorts, green leggings, and red-topped, black boots with a crenelated fringe.
Ultra Boy first appeared in Superboy #98 (1962), in which he was sent back in time to Superboy's home town of Smallville to prove himself worthy of joining the Legion by learning Superboy's secret identity. In his first adventure he only demonstrated his vision powers. Later he was romantically linked for many years with fellow Legionnaire Phantom Girl. He was considered one of the Legion's 'big 3' (along wth Superboy and Mon-El) and served two terms as leader.
The names of his parents are Crav and Mytra Nah. His girlfriend on Rimbor before he joined the Legion was An Ryd; she was later murdered by Stargrave, who framed Ultra Boy for the crime. An early extension of his backstory made him the equivalent of a "hot-rodder," that is, of lower social class than many of the other Legionnaires.
Ultra Boy was a skilled actor; this, combined with his rough background on Rimbor and social standing, helped him infiltrate criminal groups where he appeared to "go bad". This skill also made him a valuable member of the Legion Espionage Squad; he was the only member without overt "spy" powers.
Between volumes 3 and 4 of the Legion, a five year gap in the chronology occurred, during which the team disbanded. During this period Ultra Boy proposed to Phantom Girl, but she was apparently killed in an accident. Now known simply as Jo Nah, he had become a smuggler and an outlaw on his homeworld of Rimbor. He rejoined the Legion after assassins destroyed an entire apartment building trying to kill him.
A later storyline in the V4 Legion Annual #1 showed his acting skills. It was shown that for years Ultra Boy had played "dumber" than he was, to not give away any advantage to his foes. When the time sorceress Glorith began manipulating Legion history, she figured only the smarter legionnaires might notice her manipulations, and thus acted to neutralize ones like Brainiac 5. She never suspected Ultra Boy would figure out her plan, which involved provoking a battle between the Legion and Mordru at the zenith of his power, which would destroy or weaken both, allowing her to pick up the pieces. Realizing what this would mean, Ultra Boy first (in a fake diplomatic blunder) prevented the Legion from attacking Mordru, then, in disguise, visited Mordru and instead provoked him into attacking Glorith. This proved successful, leaving both Mordru and Glorith severely weakened. Years later Glorith finally figured out who was responsible and in revenge sent Phantom Girl into the past, leaving Ultra Boy believing her dead. Later still the Legion found themselves on the wrong side of the law and Ultra Boy adopted a new identity as Emerald Dragon.
During the "Five Year Gap" following the Magic Wars, Earth fell under the covert control of the Dominators, and withdrew from the United Planets. A few years later, the members of the Dominators' highly classified "Batch SW6" escaped captivity. Originally, Batch SW6 appeared to be a group of teeange Legionnaire clones, created from samples apparently taken just prior to Ferro Lad's death at the hands of the Sun-Eater. Later, they were revealed to be time-paradox duplicates, every bit as legitimate as their older counterparts. After Earth was destroyed in a disaster reminiscent of the destruction of Krypton over a millennium earlier, a few dozen surviving cities and their inhabitants reconstituted their world as New Earth. The SW6 Legionnaires -- including their version of Ultra Boy -- remained.
In post-Zero Hour continuity, his background is very similar to the original. He was a gang leader on Rimbor (running a gang called the Emerald Dragons, a reference to his Five Years Later identity), before being eaten by an Ultra Energy Beast and gaining his powers from eating the creature's flesh. He initially does not join the Legion but instead joins a rival group called the Workforce, and is briefly romantically linked to Spider Girl (Sussa Paka) before meeting and falling in love with Apparition, the post-Zero Hour incarnation of Phantom Girl, when the Workforce and Legion are stranded on Planet Hell, a prison complex located inside the sun. Eventually Ultra Boy leaves the Workforce and becomes a member of the Legion.
Ultra Boy and Apparition eventually marry and have a son named Cub, just before the Legion's reality was rebooted for the second time.
The Legion was rebooted again in 2005. Ultra Boy in this version seems much the same as his previous versions but does not have a romantic link with Phantom Girl; he is in a relationship with Shadow Lass. Trained by Karate Kid in a more responsible and tactical use of his superpowers, it's known by at least Triplicate Girl that on Rimbor, "he is charged for a crime he never committed", but refuses to say more on the question. Kinder and mellower than his gruff exterior may express, he's the first one to sense Imra's displease and insecurities for being constantly neglected by hier boyfriend, Lightning Lad. This however leads to a brief affair with the Titanian girl.