Five years ago a man's voice interrupted all television and radio broadcasts. He claimed that he could hack into anyone's DNA and alter them however he saw fit. No one believed him of course but he said they would soon. A few days later people knew that he was telling the truth when several world leaders, including the president and vice president of the United States, were transformed into little girls. That was the story for the better part of two months. After the initial transformations the governments of the world put out a high reward for the person responsible for those transformations. There was a story of one person trying to claim the reward but before they could talk they were transformed into a newborn.
Over the years since it has become apparent that he has limits on his power. The only transformations he can do are human based but there is some leeway to it. For example he has transformed people so they have tails. He has even shrunk people down to ant sized or smaller. He can't transform any inanimate object like clothes people are wearing at the time. Because of this almost all stores that carry clothing have instituted a policy of giving someone a free set of clothes if they're transformed while in the store or on store property. He can't turn someone into an animal. Other than those limitations it seems that the only limitation he has is his imagination. He can also transform many people at once in different locations with different transformations. And he seems to enjoy toying with some of those he transforms changing them multiple times.