He appeared in early "Our Gang" comedies, but he is best known for the role of Billy Batson in the 1941 motion picture serial, and first comic book superhero film, Adventures of Captain Marvel.

One newspaper story described Coghlan's rise to fame this way: "When the boy was seven years old, his great mop of hair, freckled face, genial grin, and likable personality attracted the attention of several directors who urged his parents to permit him to engage in screen work.

Mrs. Coghlan finally consented and one day he was cast for a 'bit' role in Goldwyn's Poverty of Riches, in which he played the son of Leatrice Joy.

A newspaper article at the time reported that Coghlan, "like every other young and red-blooded American, desires to arrive at manhood as soon as possible.

"[6] Coghlan's final film on his four-year DeMille-Pathe contract was 1929's military academy drama Square Shoulders.

Conceived as a silent film, Square Shoulders was transformed into a "talkie" by the expedient of adding sound to the final reel.

A 1929 newspaper story on Coghlan noted that the twelve-year-old actor was "recognized by the motion picture public as the leading juvenile screen player in the world.

In the classic 1931 gangster film The Public Enemy, Coghlan played the role of James Cagney's character, Tom Powers, as a boy.

Coghlan played the role of Shorty, a sickly boy who was sent to a state industrial school where children were forced to work at hard labor, ending up in solitary confinement.

Coghlan had another starring role in the 1932 film serial The Last of the Mohicans, based on the James Fennimore Cooper novel.

In the shorts, Coghlan played Sonny Rogers, a star baseball player and high school class president.

Coghlan also had large roles in other features through the mid 1930s, including Kentucky Blue Streak, a 1935 crime drama about a jockey who was wrongfully imprisoned and escapes to ride in the Kentucky Derby; The Little Red Schoolhouse, a 1936 drama in which Coghlan plays the lead role, a 17-year-old who runs away to New York City; and Red Lights Ahead, a 1936 comedy in which he plays the son of an eccentric father who invests in a gold mining scheme.

Although both could swim, director Aubrey Scotto wanted realism, and each time Coghlan would try to save the 195-pound (88 kg) Arnold, "both would sink and come up sputtering for breath.

[9] In 1941, the 25-year-old Coghlan revitalized his career, landing the part of Billy Batson in the Republic Pictures serial Adventures of Captain Marvel.

"[2] The 12 episodes of the "Adventures of Captain Marvel" "marked the first time a comic book superhero was depicted on the big screen.

[10]Coghlan achieved the rank of Lieutenant Commander and was often assigned as a liaison and technical advisor on motion pictures, including PT 109, The Caine Mutiny, The Bridges at Toko-Ri, Mister Roberts, and In Harm's Way starring John Wayne.

[9] His later work included appearances in the television series The Beverly Hillbillies and Dragnet and a small role in the 1966 feature The Sand Pebbles.

[12] At the time, he lived in Sepulveda in the San Fernando Valley (the area is now known as North Hills) with his wife, Betty, and their five children (sons Michael and Patrick and daughters Libby, Cathy, and Judy).

[12] In 1971, Coghlan joined the firm of George Colletta Realty in Sepulveda, working in the listing and sale of residential, income, and commercial real estate.

[11] In 1974, he had a cameo role as a zoo employee in 'The Braggart' episode of Shazam!, a live-action CBS television series based upon DC Comics' superhero Captain Marvel.