The famous shock at the climax of part three, when one of the "dead" Martians appears to lurch at its discoverers from the just-opened forward section of the capsule, was not in fact planned by director Rudolph Cartier but was the result of a lucky accident when the Martian prop slipped down from its position unexpectedly, resulting in giving the creature the semblance of movement and causing the actors - and audiences at home - to draw back in fright.

Noel Howlett (Vicar Gilpin) reprises his role in the film adaptation Quatermass and the Pit (1967), the only actor to do so.

The special effects explosive charge used for the final explosion was so powerful that Cec Linder had to stand between it and the camera, otherwise the camera might have been damaged. Linder also had to be wet down and don fire-resistant clothing and eye-pads to prevent being burnt by fire or blinded by the flash. As a result, he had to reach his mark without being able to see it!

Malcolm Watson is the only actor to have appeared in all three of the 1950s Quatermass serials.

Both André Morell (Professor Bernard Quatermass) and Richard Shaw (Sladden) were asked to reprise their roles in the film adaptation Quatermass and the Pit (1967). However, Morell was not interested in repeating himself while Shaw was unable to do so because of a prior engagement.

Michael Ripper (Sergeant) previously played Ernie in Quatermass 2 (1957), the Hammer film adaptation of Quatermass II (1955).

The original filmed inserts were edited into a two part compilation for a repeat broadcast in 1960 and still exist today.

Michael Gough was on the shortlist for Captain Potter. The role eventually went to John Stratton.

André Morell had previously been approached to appear in the second Quatermass serial, Quatermass II (1955) after Reginald Tate's sudden death. The part eventually went to John Robinson.

Paul Whitsun-Jones was asked to reprise his role as James Fullalove from The Quatermass Experiment (1953) but was busy on another project. He was replaced by Brian Worth.

Captain Potter was originally named Captain Archer.