When we’re introduced to Data in the premiere episode of Star Trek: The Next Generation, he’s a lieutenant commander and third in command of the USS Enterprise. That never changes during the show’s seven-season run. When it ends, he’s still stuck at the same rank. That wasn’t, however, the original plan.
During the course of the show, Data (Brent Spiner) was supposed to receive a promotion to Commander and then take Commander Riker’s (Jonathan Frakes) place as the Enterprise’s new second in command. He’d have been Captain Picard’s Number One for the last two seasons of the show.
It was slated to happen in the Next Generation season 6 episode “Second Chances”. As the episode played out on television, the crew of the Enterprise discovers a duplicate version of Will Riker, who was stranded on a planet years ago before Will got promoted to Commander and before he got his post aboard the Enterprise. The other Riker takes on the name Lieutenant Commander Thomas Riker and goes on to live a separate life before being sent to die in a Cardassian prison years later on Star Trek: Deep Space Nine. But it almost happened differently.
The original plan for “Second Chances” was for Will Riker to be killed off by the end of the episode. Thomas Riker would then have taken his place as the ship’s new Operations Officer with Data being promoted to the rank of Commander and taking over as Captain Picard’s First Officer.
It was a risky move, the kind of risky move television shows just didn’t make then. Though it was in the script, the show’s producers got nervous and showrunner Michael Pillar vetoed the idea before they could go through with it.
A few years later, Star Trek: Deep Space Nine would kill off Chief Miles O’Brien and have him replaced by a duplicate version. By then, though, the television landscape had already begun to change. Those changes in audience expectations allowed Deep Space Nine to take risks that weren’t possible when Next Generation was on the air.