Dolled-Up Installment: This film was originally an Aliens ripoff called Bug Hunt on Outpost Nine, but enough similarities between it and Heinlein's novel were noticed that the studio bought the novel's film rights to avoid a plagiarism suit and the script altered accordingly (Aliens was itself heavily based on the novel). Verhoeven claims to have only read the first two chapters of the book before giving up out of boredom.
Fake Nationality: EVERYONE playing Argentinian characters are just Americans using their normal accents. Special mention may have to go to Shujumi who in the book (as one might guess from his name) is Japanese, played here by American actor Anthony Ruivivar, who is not of Japanese descent.
Power Rangers Lost Galaxy, Firefly, G-Saviour — the armor from this movie has shown up everywhere. After getting passed around Hollywood for years several of the suits were eventually sold for use in the third movie, making this a weird circular trope.
The USM Auriga in Alien: Resurrection appears to have been made from a modified model of the Rodger Young, or one of its sister ships.
Wag the Director: Denise Richards refused to do a topless scene which wasn't in the original script. During filming, Paul Verhoeven told her that he had written new scenes for her, including a love scene, which would require nudity. Despite the fact that this was only her first big-budget film, she said no because she didn't think her being nude related to her character or the movie.
In the script, there was a scene during a FedNet broadcast showing the Mobile Infantry reclaiming Dantana, the planet where a Mormon colony was massacred, in the prelude to the Klendathu invasion.
The original prop for the Morita assault rifle was going to be made out of the M60, with various added and removed or modified parts◊ to change the look of the weapon; ultimately, the rifles were built out of the Ruger AC556 in a bullpup conversion kit. The final props do include M60 muzzle brakes, though.
In the director commentary on the Blu-ray DVD Paul Verhoeven stated showing the mutilated bodies on FedNet was to encourage more people to join the Federation, the cow being censored was due to PETA animal supporters, and the experiments on the Brain Bug were censored as it was classified information.
The idea I wanted to express was that these so-called advanced people are without libido. Here they are talking about war and their careers and not looking at each other at all! It is sublimated because they are fascists.
Word of Saint Paul: Casper Van Dien says he was often asked why a blonde-haired, blue-eyed actor would play the Argentinian Juan Rico. He suggests that his character was the descendant of exiled Germans (Argentina was famously a hiding place of German war criminals after World War II).
In Armor, Felix is asked if he joined up because the Ants nuked his South-American hometown.
Science Marches On: The planet where life doesn't evolve because it doesn't get enough mutation-causing radiation. We now know that even with zero radiation, the enzymes that replicate DNA still make mistakes sometimes.
Writer Conflicts with Canon: The controversies over the novel's ethical and political messages are exacerbated by the fact that some of the things Heinlein said about the worldbuilding in later interviews and essays don't seem to fit what is actually depicted in the novel, in particular whether "public service" in the novel's society refers to any kind of government work or only front-line military combat.