Born Jonathan Sazaki, he was just another human born and raised on Elysium. He suffered through the devastation of the Skyllian Blitz, which left him an orphan. During the recovery process, he stowed away on a departing relief aid freighter, bound for its home port, the asari colony of Lusia. "Anywhere is better than back there” was the mantra he kept repeating to himself the whole flight, all but falling out of his hiding place upon landing. The asari colonists took him in and arranged sanctuary at a nearby orphanage. Not long after, he was adopted out by an older Pureblood couple: Dasanne, a retired commando, and Maneena, a Matriarch and former political attaché.
As he grew and matured (kind of), Johnny learned the ways of the gun and general combat from Dasanne - who filled the "father" role of his parental couple - while Maneena (his "mother") stressed the usefulness of silver-tongued diplomacy. Both lessons came in handy when he decided, on his eighteenth birthday, to start a promising career as a freelance mercenary. He was given a decommissioned turian frigate, the Bangalore, and a tattoo of Athame's name in old asari script on his cheek as parting gifts (little fact: Dasanne did the inking herself). After the failed attempt to garnish business under the moniker of "Johnny THUNDERSTONE," he adopted his parents' name, M'Sonna. Business has picked up considerably since then.
It has been suggested that his unique mindset and mannerisms are directly caused by a as-yet diagnosed mental disorder, most likely induced by the stress and trauma of the Blitz.
Johnny's photoshopped appearance is based on images of Alec Newman.
A lot of Johnny's personality and mannerisms are inspired by Deadpool.