- Casting Gag: The episode "The Trap" involved a conference of the world air forces taking place in a castle that wouldn't look out of place in a Hammer Horror movie. A year before the show aired, Captain Scarlet's voice actor was in Dracula: Prince of Darkness.
- Billing Displacement: We'll let Chris Bentley explain this one (from The Complete Gerry Anderson: The Authorised Episode Guide):Although voice artist Lian Shin is credited on 20 episodes of the series, ("The Launching") features her only vocal appearance as Harmony Angel and she does not portray any other characters. For all of Harmony's previous speaking roles, her voice was provided by Liz Morgan... Harmony is seen in a number of later episodes, but this is the last time that she speaks.
- The Danza: Colonel White's real name is Charles Gray, and he is voiced by Donald Gray. Originally the actor Charles Gray was born Donald Gray but changed his name to avoid confusion.
- Defictionalization: Both catchphrases of the show have been borrowed by American private spaceflight firm SpaceX to describe its readiness for rocket launches, modified to "SpaceX Is Green" or "SpaceX Is Red".
- Name's the Same: It is rumoured that music group The Spectrum's involvement came about more or less accidentally; Gerry Anderson was made aware that their name and the SPECTRUM organisation's name might cause a trademark conflict. Rather than pick a new name or call the lawyers in, he chose to Take a Third Option and offered them the title-theme gig.
- The Other Darrin: Harmony Angel is voiced by Liz Morgan except for "The Launching", where she's voiced by Lian-Shin.
- Referenced by...:
- The show's Smash Cut style was Amusingly played with by Chris Evans in TFI Friday, where he would try to flip his head between two cameras in time with the Captain Scarlet riff.
- The Smash Cut style was also used in episode 28 of Yu-Gi-Oh! The Abridged Series.
- Apollo 440 referenced the series in their song "High On Your Own Supply", with the line "You're no Captain Scarlet, you're not indestructible".
- What Could Have Been: When the show started production, Gerry Anderson hoped to have an idea for a guest star to appear in each episode. For the pilot episode, for example, Patrick McGoohan was asked to guest star as the voice of the World President. McGoohan wasn't able to work it into his schedule, so he bowed out. Eventually Anderson scrapped the guest star idea entirely, as it was too expensive.
Trivia / Captain Scarlet and the Mysterons