(This is a completely revised and extended english version of an article published in italian in March 2013)
1. Early conceptions
In a film like 2001, a project that started with the explicit purpose of investigating the possibility of extraterrestrial life, it comes as no surprise that Kubrick decided very soon in the production to tackle the problem of how to actually depict the extraterrestrials themselves.
Kubrick and Arthur C. Clarke had met for the first time in April 1964: by the last months of that year the director had already set up a team working on hundreds of drawings about possible E.T. shapes - his wife Christiane was on board as well and worked on preparatory drawings - and in late 1965, the young and recently hired collaborator Anthony Frewin joined the team, researching on modern sculptures, paintings of German artist Max Ernst and modern art in general to try different ideas. (Here's a detailed account by Frewin about his appointment to the movie and about Kubrick fondness of Ernst; thirty years later, Ernst's influence resurfaced in a Ian Watson interview about the making of the movie that turned out to be Spielberg's Artificial Intelligence).