Tom Welling refused to wear a Superman suit in Smallville for a few reasons.
- He wanted to focus on Clark Kent’s journey to becoming Superman. The show was about Clark’s life as a teenager and young adult, and Welling felt that wearing the Superman suit would take away from that. He wanted to show how Clark struggled with his powers and his identity, and he felt that the suit would make it too easy for him to become Superman.
- He didn’t want to be typecast. Welling was concerned that if he wore the Superman suit, he would be typecast as Superman for the rest of his career. He wanted to be able to play other roles, and he felt that wearing the suit would limit his opportunities.
- He didn’t like the way the suit looked. Welling has said that he didn’t like the way the Superman suit looked on him. He felt that it was too bulky and didn’t fit his body type.
In the end, Welling’s decision not to wear the Superman suit was a creative one. He wanted to tell a different story about Superman, and he felt that the suit would have gotten in the way.
However, Welling did wear a Superman suit in the series finale. This was a compromise between Welling and the show’s producers. Welling agreed to wear the suit, but only if it was CGI-ed and only if it was shown from a distance. This way, Welling could still tell the story he wanted to tell, but he wouldn’t be typecast as Superman.