10 Star Trek Episodes That Started As Something Completely Different
4. Whispers
Whispers had a number of influences along the way, though it originally began as a very different episode. It was always due to focus on O'Brien, though the first version of the script saw him waking up one morning to find Keiko and Molly had vanished during the night. He then discovered that no one on the station seemed to know who he was. After doing some digging, he discovers that there is a Chief O'Brien in Starfleet, though he is still serving aboard the Enterprise-D.
When the story went to the writers' room, no one was much interested in the amnesia/who is O'Brien story. They then switched things around, looking to the seventies film The Parallax View, starring Warren Beatty, for inspiration. This allowed them to dial up the paranoia while bringing in the political themes that appear later in the script.
Ira Steven Behr ultimately looked as the episode as Invasion of the Body Snatchers, from the Body Snatcher's point of view. He thought there was a tragedy to the idea that the replacement had no idea about the true nature of their existence. Writer Paul Robert Coyle also managed to sneak in a reference to Ridley Scott's Blade Runner as well, with the replacement O'Brien being called a replicant.