5. Success breeds sequel ideas
Everyone knows what happened next: ET was a massive blockbuster hit, opening to a then-incredible $11 million in the US alone, and staying at the top of the box office charts for a startling six weeks.
Even more impressively, it was released on June 11th 1982 across the pond, and stayed either at first or second position until January the next year, earning $359 million in domestic tickets.
Roger Ebert proclaimed it as an instant classic, saying, "This is not simply a good movie. It is one of those movies that brush away our cautions and win our hearts."
Hershey, which had switched in its Reese's Pieces chocolates, saw profits surge 65% off the back of the movie's success.
And such was its impact that the movie was re-released in 1985 and scored another $40 million from American audiences.
At the 55th Academy Awards, it was nominated for nine Oscars and while it lost out to Gandhi for Best Picture, even that film's director, Richard Attenborough was certain it would scoop the prize.
ET still went on to scoop four Oscars, including score, sound and Visual Effects.
In 1994, it was selected for preservation by the US National Film Registry.
But let's go back to July 1982, with Spielberg and Mathison considering sequel ideas.
With the film already a massive success, it was seemingly natural for the writer and director to be pondering a follow-up - these days, the studio would have greenlit another film within hours of the first box office figures.
Yet the pair were hesitant. Could they replicate the ingredients that made ET work so well?
It's here that the darker themes of Night Skies began to creep into their minds again, as the pair ramped the tension for a nastier tale of alien encounters...
Next: The story, part one