He was 93, and he died of natural causes, according to his son Patrick.
Junior Coghlan, as he was usually billed, did not actually become Captain Marvel in the 12-part serial "Adventures of Captain Marvel," which Republic Pictures released in 1941. He played Billy Batson, the boy who meets a shaman in Siam that teaches him to transform into the superhero.
It was Tom Tyler who emerged as Captain Marvel, after Billy's "Shazam!" moment with a giant flash and a billow of white smoke. Coghlan was 25 at the time, but his youthful looks and rather high-pitched voice allowed him to play the younger character.
Billy the boy and Captain Marvel, in a tight red costume with a yellow lightning bolt on his chest, would morph back and forth during the 15 to 20 minute long episodes.
"It's considered by many aficionados as the best cliffhanger serial of all time," said Bruce Goldstein, director of repertory programming at Film Forum, a movie house in the South Village. "What a great fantasy for kids: a kid who turns into a superhero."
Junior Coghlan had already made his name in movies when he was a child. Starting at 3 as a crawl-on in a Western serial called "Daredevil Jack," he had been an extra, played bit parts or had significant roles in more than two dozen silent movies.
In 1925 director Cecil B. DeMille signed little Frank to a five year contract. In one of his first talkies, Coghlan played James Cagney's hoodlum as a boy in "The Public Enemy" (1931) depicting a criminal's rise in the Prohibition era.
Coghlan served as a naval aviator in World War II. He later headed the Navy's motion picture cooperation program acting as a liaison with Hollywood studios. After 23 years in the Navy, he returned to acting in bit parts in movies, on television, and in commercials.