powered by AFI
Actress Loretta Young provides a running voice-over narration for the film, as her character, "Ellen Jones" thinks about the events that are happening in the story. Actors John Hodiak and Will Geer were included in early Hollywood Reporter production charts, but neither were in the completed film. Hodiak was to portray "Dr. Ranney Grahame," a role taken over by Bruce Cowling a week after filming began, and apparently reduced after Cowling was cast. A Hollywood Reporter news item on April 21, 1950 noted that Regis Toomey was to have a featured role, but he was not in the picture. Another news item noted that director Tay Garnett was loaned to M-G-M by Thor Productions.
According to an M-G-M press release, the studio received special permission from actor William Boyd to use his "Hopalong Cassidy" image and references to his popular television series of the same name. The series, which was initially broadcast from June 24, 1949 through December 23, 1951, remained in syndication for many years and was one of the medium's first large-scale successes. In Cause for Alarm!, the character played by child actor Bradley Mora, is dressed in a Hopalong Cassidy costume, calls himself "Hoppy" and makes several references to the character's popularity on television.
Although an April 18, 1950 Hollywood Reporter news item noted that Cause for Alarm! marked the 100th feature film appearance by character actor Irving Bacon, Bacon had actually appeared in more than three hundred films prior to 1950. Many of the film's exterior scenes were shot in Beverly Hills, CA, north of Wilshire Blvd. Producer and co-screenwriter Tom Lewis was married to Loretta Young at the time of the film's production. Lewis also produced Young's popular NBC television series Letter to Loretta (later known as The Loretta Young Show), which ran from 1953 through 1961 and often featured Young in roles similar to "Ellen" in Cause for Alarm!