Superman was originally considered for this project, however, when National Periodical Publications (now known as DC Comics) turned Republic down, the producers made the offer to Fawcett Comics for their top character and was accepted.
The cast member under the Scorpion's hood, momentarily visible and identifiable when he is accidentally unmasked in one episode, is not the same actor who is eventually unmasked as the actual Scorpion in the final episode.