The Adventures of the Fly comic book series was created by Joe Simon and Jack Kirby who wrote and drew the firt four issues.. He first appeared in The Double Life of Private Strong #1 however his origin story and first "full length" appearance were in Adventures of the Fly #1.
Late one night, Tommy Troy put on a ring with a fly-shaped emblem he found in his adopted parents' attic. His parents were wizards, and the ring summoned Turan, one of the Fly People that, ages ago ruled the Earth. They used magic in their wars, and in the ultimate war they reduced most of their population to common houseflies. Only a few Fly People escaped to another dimension, where they waited for "one person... pure of heart" to fight crime and greed, which was their own downfall. Tommy was that person. By rubbing the ring and saying "I wish I were the Fly," he exchanged bodies with the other dimension and became a costumed adult superhero. To return to his own identity, all he had to do was utter his name.