Robert Wise used a single set to create Wildfire's color-coded corridors, repainting it for scenes that take place on the different levels. Wise would use this trick again in Star Trek: The Motion Picture. When filming the scene where Dr. Ruth Levitt has an epileptic seizure due towatching a blinking red light, care had to be taken when choosing the frequency of the blinking, so it was the least likely frequency to induce seizures among susceptible viewers in the theater audience.
The cast of characters in the novel was modified for the film, most notably by changing the male Dr. Peter Leavitt in the novel into a woman, Dr. Ruth Leavitt. Screenwriter Nelson Gidding suggested the change to Wise, who at first was not enthusiastic, as he initially pictured the sex-changed Dr. Leavitt as a largely decorative character reminiscent of Raquel Welch's character in the 1966 film Fantastic Voyage. When Gidding explained his take on Leavitt, Wise resolved the question in an appropriately scientific way by asking the opinion of a number of scientists, who were unanimously enthusiastic about the idea. Eventually Wise came to be very happy with the decision to make Leavitt female, as Kate Reid's Dr. Leavitt turned out to be, in his words, "the most interesting character" in the film． Another minor change was the character of Burton in the novel, who became Charles Dutton in the film; no reason was given for this name change.
A young Michael Crichton makes a cameo appearance in a non-speaking role during the scene where Dr. Hall is told to break scrub because he has to report to Wildfire, the government's secret underground research facility.
矛盾が生じない場合でも、過去の改変が未来に与える影響を扱った作品も多い。これには些細な過去の改変がバタフライ効果のように連鎖しながら拡大波及し、未来の方向性を大きく変更してしまうとする立場と、些細な改変は一時的なゆらぎに過ぎず、その後は収束し未来の方向性に大きな影響を与えないとする立場がある。SF作家のポール・アンダースンは、歴史に大きく関わる人物の暗殺や史実の妨害など、未来社会に重大な影響を与える歴史の改変を防ぐための組織のアイデアを、オムニバス長編『タイムパトロール』（Gurdians of Time、1960年）で発表した。またこの小説では「歴史が改変可能であるならば、何をもって正しい歴史とするか」という疑問も提示されている。
