Flash is actually from Titan; the largest of Saturn’s many, many moons.
Titanics have a similar, bipedal appearance to humans, but are very different physiologically.
Their green, hairless skin and larger cranium (complete with antennae) quickly distinguish them from humanity; as do the second, smaller set of arms.   Their primary arms grow from the top of the torso, from the shoulders (like humans have); but a secondary set of arms grow below that.  While not as functional as the primary set, neither are these arms vestigal; serving more of a utility function.   Used in body expression, and holding items, for example.
Titanics evolved from the ubiquitous, mega- insectoid life forms that proliferate Titan; filling many of the niches that mammals held on Terran earth.


This Alien is definitely a Daredevil at heart.    Flash was a famous, and very popular, athlete on Titan, having competed in, and mastered, many of the Tatanic sports.
He’s generally a friendly (and sometimes ‘goofy’) guy, who takes ‘having fun’ quite seriously.

‘Flash Bang’, of course, is not his native name ... but it is, in the human tongue, a good enough similarity.  And it is often joked that it resembles his athletic and thrill seeking nature: they way he can, and often does, explode into action (like the traditional flash bang grenades used by many military cultures across the solar system).
           ... and, OOC, pays homage to ‘Flash Gordon’: that 50’s icon of the Atompunk genre). 


Flash came to the attention of Danger Patrol during a terrorist incident at a major Multi-Moonal sports competition; when Stygian Adepts staged an insurgence that held hundreds of sports fans (Flash's fan, as far as Flash was concerned) hostage.
Flash led a few of his fellow athletes against the insurgents, at about the same time Danger Patrol turned up to deal with the incident.  It resulted in the two groups working together to free the hostages and overcome the Stigean terrorist cell.

After which, Flash was offered a position with the esteemed Heroic Organisation; one that he readily accepted.