They are created, not born or through choice. They undergo a secretive initiation process which includes being beaten in a dark basement with a wet pool noodle. After they are beaten severely, they are broken down physically and mentally to be rebuilt as the ultimate tool in Forum Moderation. Each Potential Ninja must pass a rigorous test of physical fitness, wit, and survival skills. This test takes place deep inside the Cambodian jungles.
The physical fitness test is different for each Potential Ninja, but always includes wrestling a tiger and beating it to death with nothing but your bare hands.
The Trial of Wit involves solving a Mayan Death Riddle to unlock a chamber which holds a Crystal Skull. The Potential Ninja must then take this Crystal Skull deep into the bowls of Bungie HQ to be stored for purposes known only to Bungie Employees.
The Trial of Survival includes being injected with a lethal toxin known only as "1337" which will kill the Potential Ninja in exactly 1 hour. In order to survive, the Potential Ninja must journey to the heart of the Cambodian jungles and fight their way through drug cartels, poison mutant snakes, and tigers. At the center of the jungle lies the Antidote that will save their life...being guarded by a Yeti! If they are skilled enough to survive this ordeal, they are welcomed among the ranks of the Forum Ninjas.