jackalopingintothevoid:

A concept: The Spartan-II program is rejected. The Covenant never arrive. The Spartan-II candidates are never stolen from their homes, never trained to be hyper-intelligent killers. They carry on living their ordinary lives, but they never stop being extraordinary people. By the year 2558, John has still managed to become well-known and well-beloved by the general public, especially the Outer Colonies.

As Space Steve Irwin.