- Actor-Inspired Element: According to Audrey Hepburn, the scene where Regina spills ice cream on Alex's suit is based on a real-life accident where Hepburn spilled red wine over Cary Grant's suit at a dinner party.
- Follow the Leader: Universal tried to recreate Charade's success with Mirage (1965), which is Darker and Edgier but shares many of this film's elements: It's a Thriller with a twisty plot, Witty Banter, a snappy One-Word Title, and a MayDecember Romance between the two leads. The films also have screenwriter Peter Stone and actors Walter Matthau and George Kennedy in common. In 1966, Universal made two more similar films, Arabesque (also scripted by Stone) and Blindfold (whose supporting cast included Ned Glass from Charade).
- Public Domain Feature Films: Charade is on the list, due to Universal not putting a full copyright notice on the film — namely, they omitted to put a "Copyright", "Copr." or "©" in the notice, which was required by law for the work to be copyrighted. For once, Screwed by the Lawyers actually works out in the favor of film fans! (However, the soundtrack music is still under copyright outside the context of the film.)
- Real-Life Relative: During the dance game in the nightclub, Audrey Hepburn's husband, Mel Ferrer, can be seen briefly in the background, smoking a cigarette.
- Wag the Director: A positive example. Cary Grant was uncomfortable about the age gap between himself and Audrey Hepburn (he was 59 and she was 33). To satisfy his concerns, the filmmakers agreed to add several lines of dialogue in which he comments on his age and Regina Hepburn's character is portrayed as the pursuer.
- What Could Have Been: At one point, the film was going to star Warren Beatty and Natalie Wood.
- Working Title: The Unsuspecting Wife.
Trivia / Charade