Trivia: The sound of E.T. walking was made by someone walking through jelly.
Trivia: This entire movie was shot in sequence. For people that don't know much about how movies are filmed, they are usually shot out of sequence (they might do the last scene first and the first scene in the middle etc). Spielberg did this so he could get the honest reaction from Elliot when ET left at the end.
Trivia: Harrison Ford played the part of the School Principal but his scenes were cut. His wife at the time was one of the screenwriters and he visited the set regularly so Mr. Spielberg asked him to play the part. This rumor was confirmed in the 2002 20th Anniversary Limited Edition DVD book that came with the Boxset.
Trivia: Peter Coyote was cast as Agent Keys in "E.T. The Extraterrestrial" because he had impressed Steven Spielberg a few years earlier, when Coyote auditioned for the part of Indiana Jones in "Raiders of the Lost Ark." Unfortunately, Coyote tripped and stumbled during that audition (conveying an awkward and apologetic image, just the opposite of the confident and sure-footed Indiana Jones image), so Coyote didn't get the part. But Steven Spielberg never forgot Coyote and subsequently cast him in E.T.