Later that Summer, Mister Who was involved in a routine prison transfer when he managed to slip himself a dose of Solution Z and grow to giant proportions.  While easily escape from his guard, he felt conspicuous and so shrunk himself to a few inches in size to disappear among the crowd.  Reaching a car, he regained normal size but became invisible, starting the police as the car drove away.  His first target was the estate of  eccentric multi-millionaire P.J. Moogan. Crashing a gala, he slips pasts the guests, including Kent and Inza Nelson and confronts Moogan, subduing him and robbing his safe.  As he flees, Doctor Fate finds the unconscious Moogan and pursues the criminal across the lawn.  Mister Who is prepared tho and rapidly grows to 50 feet in statute and thrashes Fate, slinging him into the distance and escaping. Who then re-connects with his old gang and shares his latest plan, to break into the hospital where P. J. Moogan is being treated and replace him, using he deception to marshal Moogan's great wealth.  The plan works initially, with the crooks dragging the unconscious millionare out of his bed and Who adopting his appearance in his place. When Doctor Fate stops in to check on Moogan, the adrenaline search at seeing his old foe activates  the Solution Z in his blood stream, causing Mister Who to increase in size and remove the disguise.   Fate promptly defeats Who's gang and then finds the Villain who has shrunk in size to escape.  No match for a hero huge in size, Who is defeated and returned to prison (More Fun #79).

The next recorded case was nearly a year later in May of 1943.  The elderly Mister Who was now considered a harmless dotard, feeding pigeons on the window sill of his cell.  Unknown to his captors, the criminal was training the pigeon and when his gang sends a letter soaked in Solution Z, he shrinks in size and uses the pigeon to escape by flight.  Meeting up with his gang, Who strategized a new crime spree and expecting the arrival of Doctor Fate, concocted a variant of Solution Z that only had the ability to shrink.  Predictably Fate intercepts Who and his gang and when he is stunned by a blow to the head, one of the  gangster poses as a helpful passer-by and tricks him into drinking the formula.  Fate shrinks to the size of a small wren and Who places him in a bird cage for later torment.  After tricking the cat into releasing him from the cage, Fate races back to his Salem tower to use a gazing ball to see where Who and his men are.  Seeing them approach a clifftop mansion, Fate quickly intervenes and use his small size to activate the alarm system and summon the police.  Who and his men are routed but see a wealthy country club and rob it.  They don't get far with the ill-gotten gains before the miniature Fate again interferes.  As the hero gains the upper hand, Mister Who moves to escape but Fate, growing in size as the Z formula wears off, knocks him unconscious until the police arrive to take them all to jail.

The final fate of Mister Who on Earth-Two remains unknown.