The son of a uranium miner, Mushroom Cloud suffered from a temporal mutation as a result of his father’s exposure to radiation. Existing in simultaneous mental contact with his past and future selves, Mushroom could, at any given time, share in their knowledge.
It was this knowledge that showed to him that he was destined to die at the hands of the TIME Vaulters. In a bid to flee an inescapable fate, Cloud set into motion the events that led to the creation of Doctor Tomorrow.
Abducted by the Vaulters, with no hope of rescue, Cloud had become nothing but expendable evidence. From the chair they had strapped him to, Cloud watched the Vaulters operate their machines and he learned their intricacies. Rubbing his wrist raw to the bone, Cloud slipped from the chair and made a mad dash to the capsule just like he had done a thousand times before in his head.
With the few seconds he had left, Cloud programmed the capsule to go back as far as it could, and as soon as it began its voyage to Bart Simms in 1942, reality began to slip away. Knowing that he had succeeded in changing history, Cloud gambled that his temporal consciousness would retain the events of his past life. No sooner than he popped out his mom, he began a second life, complete with all the memories of the first.
Figuring out that Bart was the one that received the time capsule did not take long, as Bart made it too easy for Cloud once he donned the Doctor Tomorrow uniform. After his parents turned him over to the feds out of fear that evil spirits possessed him, Mushroom stayed under observation for possible military applications until he escaped and met Bart Simms, who he convinced that the rightful owners of the time capsule wanted him to watch over. Everything Cloud did was to get Bart to 1998, when history would repeat itself. The irony was that Bart’s quest did not change history, but set it right.
For most of his life, Mushroom, driven mad by the circumstances of his own death, abused drugs to keep himself from witnessing his own demise.