This is believed to be the first film ever to use the arabic numeral 2 as an indicator that it was the sequel to another film (as opposed to Roman numerals).
Brian Donlevy reprises his role as Bernard Quatermass from The Quatermass Xperiment (1955), making him the only actor to play the character on screen twice. In spite of this, he was reportedly Quatermass creator Nigel Kneale's least favourite actor in the role.
The last surviving 35mm print of the U.S. theatrical version, under the title "Enemy from Space," held by United Artists, was reportedly cut up and used for land fill.
Originally shot in AnsaColor, developed by Agfa, but released in black and white, the colour negative still exists in the archives.
In between takes Brian Donlevy's toupée was accidentally blown off by the aeroplane engine wind machines used during the film's climax.