As with most biographical films, the script is a combination of fact and screenwriters' fancy. To give but two examples, Lon Chaney Jr. was not born in a hospital, but at his parents' then-home in Oklahoma City, as was common at the time. Further, Cleva Creighton Chaney was well aware, before her marriage to Lon Chaney, that his parents were hearing-impaired, and had already met them on several occasions.
When asked by David Letterman what was his motivation for what he does, Tom Savini, the famous special effects artist and actor, said he saw this movie when he was 12 and it was his inspiration, and that he named his son 'Lon' after Lon Chaney.
James Cagney had previously acted alongside Lon Chaney's son Lon Chaney Jr. in Un lion dans les rues (1953).
Last full-length feature film of Philip Van Zandt. After this film he appeared in a few two-reel comedy shorts before committing suicide in 1958.
Although it isn't pointed out specifically, Irving Thalberg was the production chief at Universal, where Chaney made "The Hunchback of Notre Dame," but then moved to MGM, where Chaney spent the majority of his career.