- Actor Allusion: In the 2005 version, one of the actors referred to David Tennant as "Doctor" rather than his character's name, in reference to a bit of then-recent casting news.
- Missing Episode: Most of the TV version of The Quatermass Experiment is missing, because it was performed live in the days before any reliable method of recording television programs existed; only the first two episodes remain, in dodgy copies made with an experimental technology (the later two serials are preserved in full, though in Quatermass II the quality is still inferior).
- The Other Darrin: Each of the five serialsnote features a different actor as Quatermass. The original actor died, and every subsequent actor proved unavailable after completing one installment.
- Accidentally Correct Writing: In Quatermass and the Pit (1967), the protagonists uncover remains of primitive humans from five million years ago. The characters state that no such remains have ever been found back that far in time before. In 1974, Lucy would be found and she would be the oldest human/hominid remains at 3.2 million years until even earlier specimens were found, making the concept of humans being in existence five million years ago well within possibility.
- Disowned Adaptation: Nigel Kneale was not impressed with the first two films, due to the casting of the American Brian Donleavy as Quatermass and to the rewrite of the ending of the first film to the army just blowing the monster up.
- Executive Meddling: American Brian Donlevy was cast as Quatermass in the first two films so they could be sold easier in the American market.
- Market-Based Title: The films were retitled The Creeping Unknown, Enemy from Space, and Five Million Years to Earth on US release, since Quatermass wasn't a selling point outside the UK.
- The Other Darrin: Not quite as bad as the serials, but the length of time between the two fifties films and 1967's Quatermass and the Pit meant Brian Donlevy was replaced by Andrew Keir. In other words, Quatermass changes from a scowling American in his mid-fifties to a fiery Scot of barely forty. Astonishingly, it works. (Even more astonishingly, when compared with the TV version Quatermass changes from a plummy-voiced Englishman to a Scotsman, speaking some of the same dialogue.)
- You Look Familiar: Sladden the drill technician in Quatermass and the Pit is played by Duncan Lamont, who played Victor Carroon in the original BBC serial.
- Hipgnosis: Did the cover of the original band's only album.