** When Floyd drinks out of a straw in zero-g, the liquid moves back down.
** One of the flight crew leans on a chair (in zero-g) to talk to Floyd.
** The Aries lands with its cockpit windows facing upward, so the pilots shouldn't be able to see the Earth moving up past the windows. (Perhaps the windows have some kind of transparent display overlay?)
** When the Earth is seen from the moonbase at Clavius and the Monolith dig site in Tycho, it's oriented with north pointing upwards. However, Clavius and Tycho are in the Moon's southern hemisphere, so the Earth should have been upside-down (and angled proportionately to the viewer's lunar latitude).
** In some scenes where Frank or Dave are jogging around the center ring, you can tell they are not ''quite'' at the "bottom" of the set and thus are at a slight angle where they would typically be at one. This is when the camera itself is occupying that spot.
** The people wearing the shoes that stick to the floor ''try'' to walk the way they would in zero G, but in reality they would be slightly fighting the inertia of their upper bodies wanting to stay behind. Instead they just walk as if through glue.
* DoingItForTheArt: Stanley Kubrick and Arthur C. Clarke spent enormous efforts into making everything as realistic as possible. The earth moving equipment seen on the Moon would ''actually'' work on the real Moon. Quite a few experts from NASA and IBM were asked to help design the sets.
** Clarke published a few lines from his diary from pre-production in the introduction of a re-issue of the novel. They include "rang Creator/IsaacAsimov to ask him about the biochemistry of [[AscendedToCarnivorism turning herbivores into carnivores]]." (Asimov, besides writing science fiction, was a professor of biochemistry.) And they never even [[ShownTheirWork did anything]] with that...
** Kubrick required the compositing work to be done by a team of British animators painting traveling mattes by hand frame-by-frame to mask out each element, rather than using bluescreen. When production ended, most of them signed onto ''WesternAnimation/YellowSubmarine'' in order to work on something colorful after spending two years painting little black blobs.
** Instead of storyboarding the docking sequence, multiple model sequences were shot so Kubrick could ''edit them down.''
* EnforcedMethodActing: Douglas Rain was only given HAL's lines, not the full script - thus keeping the CreepyMonotone at all costs.
* FakeRussian: Brit Leonard Rossiter as Dr. Smyslov, the guy who grills Floyd about just what's going on at Clavius.
* WhatCouldHaveBeen: Kubrick had allegedly asked OsamuTezuka to work as a production designer for the film, but sadly, The God of Manga was far too busy with his own projects to oblige.
** Also worthy of note is that Kubrick approached the rock group Pink Floyd to do the music to the film (as well as the later Clockwork Orange), but they declined. Roger Waters later said not scoring 2001 was one of his biggest regrets. (Supposedly "Echoes" syncs up to the third act of 2001, try it out.)
** Early drafts had the ship powered by an OrionDrive.
* Hal is activated on January 12, 1992. The day, now passed, was not particularly notable.
* Notable, but not plot-relevant. The scene with the primates is obviously not 2001, but the title card for the Discovery mentions that it is 18 months later. This places the trip to the moon (and discovery of the monolith) in 1999.