Who's in it? Keir Dullea, William Sylvester, Leonard Rossiter, Robert Beatty, Daniel Richter.
And the director? Stanley Kubrick.
To begin at the beginning, what's this business with the apes? A film about evolution, it opens at the moment when apes take up tools, thus starting on the rocky road to humanity.
What on Earth gave them that idea? A big black monolith.
What is this monolith thing? The monolith is an otherworldly influence that either triggers evolutionary leaps, or is simply in the habit of turning up when they happen.
Suddenly it's four million years later, and the monolith turns up again. What happens this time? Buried all those years ago, another monolith is found on the moon emitting a radio signal to Jupiter.
Why Jupiter? The special effects team couldn't do a convincing Saturn.
You expect me to buy that? It's true! Ok, so we don't know why it's sending a signal there, but we send seven humans and the most advanced computer known to man, HAL 9000, to find out.
What's the trouble with HAL? HAL decides that humans are a danger to the mission and attempts to destroy them. We never learn whether HAL's error is an excuse to exterminate the crew or a genuine mistake wounding his pride. What started with an ape picking up the first tool finishes with a human switching off the last.
You make it seem quite simple, but what's all that psychedelic gubbins at the end? Alone in space without the tools he'd fashioned to get there, man faces his final challenge. A terrifying journey ends in a curiously Earthly room. Our hero sees himself first as an old man and finally dying, at which moment he sees the monolith. Having reached a point that may be interpreted as death, evolution, or both, Kubrick baffles us with the star-child, a giant human-embryo-come-planet.
Facts to impress your friends with: Kubrick wrote the film together with Arthur C Clarke using a story Clarke had originally written for a BBC competition.
Clarke denied any link between HAL and IBM (the letters which follow alphabetically from H, A, and L).
Alex North wrote an original score for the film, but Kubrick ditched it when the classical music used on the set to provide atmosphere proved so successful.
Rock Hudson is reported to have been among celebrities who also lost the plot of "2001".