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. Anthony Ruivivar's ethnic background is Filipino, Chinese, Spanish, German, and Scottish.
Power Rangers Lost Galaxy, Firefly — 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.
Recycled Script: This film was originally to be an Aliens ripoff called "Bug Hunt", then Verhoeven got the rights to the Heinlein story.
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 only hint towards the original design for the final weapon is that the props include M60 muzzle brakes.
Word of God: 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.
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.