When Hercule Poirot (Sir Peter Ustinov) examines the hotel register for signatures of previous guests, he discovers the names of several international celebrities during the 1930s, including Cole Porter, Ivor Novello, Maurice Chevalier, Fred Astaire, Adele Astaire, Charlie Chaplin, and possibly Marlene Dietrich. An entry listing a home address is listed as Berlin, although the signature is illegible aside from the capital M and D). The register is likely a private joke by the filmmakers since it appears on-screen for only a brief second or two.
This movie relocates the provincial North Devon, England setting on Smuggler's Island off the Devonshire Coast from the Dame Agatha Christie source "Evil Under the Sun" novel to an island in the Adriatic Sea "somewhere west of Suez", a setting played by the exotic Spanish island location of Mallorca. Screenwriter Anthony Shaffer once said of this: "The location is important. The island should be a star. Just as the Nile steamer (in Death on the Nile (1978)) and the Orient Express (in Murder on the Orient Express (1974)) were stars." Mallorca was also, at the time, the home of Director Guy Hamilton.
Dame Diana Rigg and Dame Maggie Smith have children who appeared together in another production based on a Dame Agatha Christie novel. Rachael Stirling (Rigg's daughter) and Toby Stephens (Smith's son) appeared in Poirot (1989) season nine, episode one, "Five Little Pigs".
The characters of Mrs. Castle and Rosamund Darnley in the source Dame Agatha Christie's book "Evil Under the Sun" were merged to be one character for this movie, Daphne Castle (played by Dame Maggie Smith).
The game that Odell Gardener (James Mason) is playing when Hercule Poirot (Sir Peter Ustinov) asks him about his whereabouts during the murder is pétanque, a French game in which players have to throw hollow metal balls as close as possible to a wooden one.
The characters of Reverend Stephen Lane and Major Barry in the source Dame Agatha Christie's novel "Evil Under the Sun" were removed for this movie adaptation. Other minor characters were also dropped.
Despite being cheaper, less starry and less ambitious than its two predecessors - "Murder On The Orient Express" and "Death On The Nile", both big hits - this film was a huge money-loser and put an end to the Agatha Christie franchise of producers John Brabourne and Richard Goodwin.
After The Mirror Crack'd (1980), this was the second and final Dame Agatha Christie adaptation directed by Guy Hamilton. Hamilton directed the movies consecutively and, prior to the first movie, had not been "totally enamored" of the Christie books.
This movie was selected to be the 1982 Royal Film Performance. This movie screened on Monday, March 22, 1982 at London's Odeon Theatre, Leicester Square in the gracious presence of Her Majesty Queen Elizabeth II with proceeds from the charity U.K. premiere going to the Cinema and Television Benevolent Fund. However, this screening was not the world premiere of the movie, it had debuted in Australia a month earlier in February 1982, this movie launching down under there because EMI's Can't Stop the Music (1980) had had its best box-office returns there.
Early in the film when when the Island appears, Roddy McDowalls' character Rex Brewster is talking to Maggie Smiths' character Daphne Castle about the play that Diana Riggs' character Alena Marshall has just appeared in "Hail and Farewell". That is play that Groucho Marx is trying to get backing for in Room Service.