There are two films I desperately wanted to write sequels to: Wargames and The Day The Earth Stood Still. They're both Cold War parables in which all of our struggles amount to nothing in the face of superior intelligence and the only thing that saves us from armageddon is the compassion of the superior force. Both films end as cautionary tales: WOPR/Joshua isn't removed from service (as far as we can tell; he opts not to start nuclear war because he sees it as futile. Klaatu doesn't wipe out the human race because we're left with a warning to shape the fuck up or he'll come straighten us the fuck out. In the story DTESS is based on ("Farewell to the Master"), the real power is Gort - Klaatu is just this omnipotent robot's servant. I wanted to write a DTESS in which Gort has been sitting there, immobile, on the Capitol steps since 1951, unnoticed and disregarded as the Global War On Terror engulfs us all... then suddenly he's gone and key people start disappearing. I wanted to make a terrorism parable tie-in to the Cold War parable Robert Wise gave us. Instead we got Keanu Reeves and global warming. I wanted to write a Wargames in which... well, not this. Oh well.
The Wargames video game for PC was pretty damn fun on top of it being a good movie.