Billing Displacement: STARRING FARRAH FAWCETT — TV Guide ad. Except Jenny Agutter was the female lead, and Farrah's role was a minor part as an assistant in a face-lift shop.
Dawson Casting: Michael York was already in his late thirties. Jenny Agutter was 24, playing a 17-year-old. The main reason the death-age was raised, from 21 in the novel to 30 in the movie, was because the actors chosen to play the roles could never pass as teen-agers. Richard Jordan (Francis 7) was 38 years old during filming. This also bypasses issues with the limited hours younger actors can work— not to mention the uncomfortable implications for some of sexually-active 14- and 15-year-old "adults".
Executive Meddling: The powers that be insisted that many important scenes be cut so the result would be rated PG. We still get a quick glimpse of some bare ta-tas, though. Think of it as Movie Ratings March On. PG used to be much more permissive before the creation of the PG-13 rating.
Try to explain the plot of the movie to somebody who hasn't seen it. "Um, in a dystopian future, there are cops who hunt people down for trying to exceed their government-mandated lifespans ..." Similarity to any later film is a coincidence.
Throw It In: In the final scene when the crowd is gathering in awe around the Old Man, one of the extras gives the Vulcan salute that is of course familiar from Star Trek. The director probably either didn't recognize it or didn't mind it in the least. At the time this film was made, Star Trek was still just some obscure cancelled TV show from The Sixties and had yet to catch on with the general public. It wouldn't have it's own official revival until three years later.