Jay Kirby，American actor best known for a short string of Hopalong Cassidy Westerns in the 1940s in which he played Cassidy's youthful sidekick Johnny Travers. Kirby was born William B. George in Missouri. He began acting in films in 1942 when he was cast to replace Russell Hayden in the Cassidy films. He served briefly as an aviation cadet in the U.S.