Knockout actually features a couple of actors who were former professional boxers. Noble Kid Chissell was a lightweight with a record of 1-8-1 and played the punch drunk Hawkins that Johnny has an exchange with in the locker room before his first fight in the film. Frank Riggi was a heavyweight with a record of 22-10-6 and played Monk Hanson the fighter who Johnny faces at the end of the film, and Riggi was also the boxer that John Garfield's character faced at the conclusion of They Made Me A Criminal.
Arthur Kennedy and Anthony Quinn both appeared in "Lawrence of Arabia" some 20 years after this picture was made.
This film's earliest documented telecast took place in Tucson Monday 8 October 1956 on KDWI (Channel 9); it first aired in Boston Thursday 22 November 1956 on WBZ (Channel 4), in Sacramento CA Friday 14 December 1956 on KCRA (Channel 3), in Indianapolis Tuesday 18 December 1956 on WISH (Channel 8), in Wichita Tuesday 19 February 1957 on KAKE (Channel 10), in Miami Monday 20 May 1957 on WTVJ (Channel 4) and in Portland OR Saturday 28 September 1957 on KOIN (Channel 6).