[2] Rokk Krinn, best known as Cosmic Boy, is a founding member of the Legion of Super-Heroes, along with Lightning Lad and Saturn Girl who possesses the innate ability to generate magnetic fields.

In the pre-Zero Hour Legion, Cosmic Boy is romantically involved with Night Girl (Lydda Jath), whom he eventually marries.

After cutting ties with his corrupt manager, Alex Cuspin, Rokk joins the Legion of Super-Heroes as Cosmic Boy.

After seemingly destroying the Dominators' homeworld (he actually sends it to the Phantom Zone), Cosmic Boy is voted out of office, being replaced by Supergirl.

[4]In Doomsday Clock, Cosmic Boy is among the Legionnaires who appear in the present after Doctor Manhattan undoes his alterations to the timeline, restoring the Legion and the Justice Society of America.

[5] In The New Golden Age, Cosmic Boy is among the Legion of Super-Heroes members who arrive in the present and confront the Justice Society over their decision to recruit Legionnaire, a young, heroic incarnation of Mordru.

A tie-in to the Legends limited series, it was written by Paul Levitz, with art by Keith Giffen, Ernie Colón, and Bob Smith.

They find themselves threatened by many citizens and residents of the United States, who have been manipulated by Glorious Godfrey as part of Darkseid's scheme to discredit Earth's superhero community.

He and Night Girl review videotapes of recent history, including references to the bombing of Hiroshima, the explosion of the American space shuttle Challenger, and the meltdown at the Chernobyl nuclear power plant, but no mention of Superman's early career as Superboy.

Cosmic Boy magnetically catches the payload and sends the debris harmlessly toward the ocean, but American soldiers assume that he is a foreign spy.

Seeking to protect the satellite, Cosmic Boy and Night Girl travel to NASA facilities in Houston where they meet Jason, one of the astronauts who designed the shuttle.

They are unaware that the last name of Jason — the astronaut they just met — is Krinnski, which implies that he may be a distant ancestor of Cosmic Boy, whose real name is Rokk Krinn.

Cosmic Boy and Night Girl return to the 30th century, where time travel experts Brainiac 5 and Circadia Senius may be able to determine the problem.

Realizing that they need a massive power source to propel the Bubble to the 30th century, Cosmic Boy harnesses energy from Earth's magnetic field.