It is possible that HAL made a mistake well in advance of his forehead-slapping blunder over the antenna unit. When playing chess with Poole, HAL should have called his fifteenth move as Queen to Bishop six, not Queen to Bishop three, accord in to chess expert Murray Campbell. While it's possible this is simply an error in the script, many have read it as super sneaky foreshadowing on Kubrick's part, especially given that the director was an avid chess player. Or that HAL was testing Dave's intelligence by deliberately making a wrong move and seeing if he noticed. (Source)

HAL's unusual choice of his last song it is a shout-out to the IBM 7094. In 1961, the 7094 was the first computer to use its synthesized voice to sing. The song the programmers chose was none other than "Daisy Bell." Arthur C. Clarke witnessed a demonstration of the 7094's capabilities and wove this little bit of computer history into HAL's backstory. (Source)

The first 25 minutes of the film has no dialogue. The final 23 minutes, not counting the credits, also goes by without a word. In total, roughly 88 minutes of the film gives the viewer the silent treatment. For our mathematically inclined readers, that's about 55 percent of its runtime, making it the yin to Michael Bay's yang. (Source)

Kubrick's filmmaking techniques in 2001 were so convincing for the day that some conspiracy theorists have claimed he was hired by NASA to fake the 1969 moon landings. As part of the supposed deal, Kubrick was offered VIP access to Roswell, New Mexico, where he no doubt saw all manner of ET craziness. (Source)

Arthur C. Clarke has placed his mark on science fact as much as science fiction. In 1945, he wrote a paper titled "Extra-Terrestrial Relays—Can Rocket Stations Give Worldwide Radio Coverage?" The paper popularized the idea of using geosynchronous orbit—an orbit that matches the Earth's rotation so objects in it appears to stay in the same place—for communications spacecraft. Today we use this orbit for our communications satellites, and it is often referred to as a Clarke Orbit in honor of the author. (Source and Source)