 In later years , Hubbard asserted that the 1955 film Mister Roberts was based on his service aboard the USS Algol with Henry Fonda 's eponymous character being based on Hubbard himself and James Cagney 's tyrannical character based on the commander of the Algol . In a February 1956 lecture , Hubbard told Scientologists : " There was a story made about that vessel [ the Algol ] , by the way . It was called Mister Roberts . You may have seen this picture or read the book . " According to a Church of Scientology publication , 
