In the 20th Century, Lex Luthor discovered a process known as the ‘Bizarro Matrix’ which created the original grotesque duplicate of Superman. During the Legion’s prolonged stay in the 20th Century, and unknown to the rest of the Legion, Brainiac 5.1 stole the secret of the Bizarro Matrix from Luthor. Back in the 30th Century, Brainy used his the process on the Legion Outpost and, as a result, accidentally transformed all the occupants of the base into Bizarro versions of themselves. Each Legionnaire became grotesque and deranged, although most still had their powers.
Invisible Kid only escaped because he was invisible and unaffected by the bizarro process. He was captured by the other Bizarros but, by half-disappearing to give the appearance of being a skeleton, he fooled the hapless Bizarros into accepting him. Invisible Kid and Bizarro-Koko set about finding a cure and it was the bizarro monkey who separated the host DNA from the transformed DNA that was taking over the Legionnaires. Using what Koko had discovered, Invisible Kid transmitted the modified rays directly to the Bizarros’ omnicoms. The split of DNA, however, produced two beings out of one: the Legionnaires and their bizarro counterparts now existed simultaneously. The real Brainiac 5.1 used his restored shrink gun to reduce all the Bizarros to tiny size and incarcerated them in a miniature sealed environment. Strangely, when the real Koko was restored, Bizarro-Koko joined with the other Bizarros and ended up being shrunk with his master. A sad reward for the genius who saved the Legion.
