It's probably not something you'd notice unless it was pointed out to you, but almost every adult seen in the movie are only filmed from the waist down. The effect allowed every audience member, no matter what age, to feel like a child going through Elliot's experience.
Another interesting filming technique was to shoot the entire movie in chronological order, something that is rarely done. Spielberg did this to create a more realistic and emotional reaction to E.T. For the children. They met, got close to, and mourned E.T.'s departure with a natural progression.
E.T. Came from Spielberg's own imaginary alien friend that he created when his parents divorced in 1960. From that sad time, the lovable and friendly "E.T." was created with the help of Melissa Mathison who helped Spielberg write the script while on the set of "Raiders of the Lost Ark."
