How "2001" Became the Space Odyssey We Know
James Cameron narrates this documentary on the classic film 2001. It includes archival footage of the late Arthur C. Clarke in the 1960s touring spacecraft manufacturing facilities, footage of designers putting together models, snippets of archival footage of Kubrick, interviews with various luminaries, and various other amazing stuff I've never seen. It also features interviews with Doug Trumbull and others who did special effects for the film. If you're a 2001 fan, this is 43 minutes of candy.
Skip to 7:00 to find out how they did the floating-pen trick -- including an interview with the actress who played the "Space Hostess" who grabbed the pen seemingly from midair. Skip to around 11:00 to meet the guys who played the apes (!). Around 13:45, Clarke explains how the monolith originally was to have a movie screen on it (!!).
See also: “2001? Trailers, Then and Now.