
He was initially a well-known child actor in the 1920s and 30's.

He was the voice of Lampwick, Pinocchio's friend who becomes a donkey in
Disney's Pinocchio. 
His parents were The Flying Johnsons, a Flying Circus act with the Sells Floto Circus. It was a profession that his father attempted to train him in as well but Frank's fear of heights became a problem.

His most important was the lead in
Wild Boys of the Road, about indictment of aimless teens vagabonding across America during the Depression. He co-starred with Gene Autry in Autry's first starring film,
The Phantom Empire.

Darro served in the US Navy Hospital Corps during World War II where he contracted malaria.

He had three wives (not at the same time of course), his parents had divorced when they were in the circus.

He died of a heart attack at the age of 59 on Christmas Day in 1976 while visiting friends in Huntington Beach, California.