Star Trek: The Next Generation had many iconic villains throughout its run, though few were as memorable as Data's "brother" Lore. The misguided Synth created before Data by Dr. Noonian Soong gave Data, Picard, and the rest of the crew plenty of trouble throughout the series, but apparently, that wasn't originally the intention for the character. In fact, Lore was originally envisioned to be an almost entirely different character, according to author and avid fan Larry Nemecek.
Larry Nemecek, author of the book Star Trek: The Next Generation Companion revealed (via RedShirtsAlwaysDie.com) that Lore ended up being an entirely different character than was originally conceived. Read on about the original plan for Lore, and how it ended up inspiring another character.
Lore was originally planned to be a female android, to provide a love interest for Data. Her job would have been to go out and repair dangerous situations. It was Brent Spiner who suggested the old 'evil twin' concept be used instead. The female android concept was later used in the third season episode 'The Offspring,' although this interpretation had the new android as Data’s “child” rather than a potential love interest.
Lore wasn't just envisioned as a female Synth, there wasn't even a plan for her to be a villain. Luckily plans changed, and Star Trek: The Next Generation fans got the villain version of Lore, who went on to have a few high-profile encounters with the Enterprise crew. The concept for the original character resulted in "Data's daughter," which was used by the series in a later episode.
It's also worth noting that the concept of Data's daughter was ultimately used as the primary story for Star Trek: Picard Season 1. It's interesting to see the ripple effect of the change in plans and think about how different both Star Trek: The Next Generation and Star Trek: Picard would be had writers and producers stuck with their original plan for Lore.
Speaking of which, it's worth mentioning that Star Trek: The Next Generation never definitively explained what became of Lore. Due to the Synth-heavy storyline of Season 1 of Star Trek: Picard, it was speculated that Lore would make a triumphant return to the franchise, but that didn't happen. It's possible he could one day re-surface in the franchise, though given Brent Spiner's advanced age and the agelessness of Synths in the Star Trek universe, it feels a little unlikely.
Perhaps Lore will have an appearance in one of the new upcoming Star Trek shows, but we can only wait and see. It's worth noting that many former Star Trek characters are already slated for Star Trek: Picard Season 2, and even someone we wouldn't expect. Perhaps it's not so crazy to assume Lore's return is unlikely as I just mentioned? Only time will tell.