The mystery of Rey's parents was one of the biggest questions to come from the release of Star Wars: The Force Awakens. And with the confirmation that she was Rey Palpatine in Star Wars: The Rise of Skywalker, many felt disappointed with the lack of hints pointing towards this revelation. However, re-watching the sequel trilogy with the surprise in mind reveals possible foreshadowing for Rey's dark lineage.
Star Wars: The Last Jedi gave the Rey mystery a twist, as Kylo Ren said her parents were "filthy junk traders who sold [her] off for drinking money." While the idea that Rey came from no one important could've worked, there were still hints that all wasn't as it seemed. The amount of power Rey had before being trained felt very unnatural, as it was clear her connection to the Force was just as, if not stronger than Luke's connection in Star Wars: A New Hope.
Hints to the Sith darkness in her are also given when Rey meditates with Luke on his island. As she feels the pull of the underground cave, Luke says, "You went straight to the dark... It offered something you needed, and you didn't even try to stop yourself." While at the time, it felt like Rey was simply desperate for answers, looking back, it's clear that the Palpatine blood within her has a natural pull to the dark side.
When Rey is finally compelled to enter the cave, she comes face to face with a mirror and begins seeing illusions of herself. She asks the mirror to show her parents, and two shadowy figures approach, only to form into a reflection of herself. While the ambiguity of the scene leaves it up for interpretation, a Reddit theory speculates the moment is foreshadowing the Palpatine clones.
Confirmed through The Rise of Skywalker's novelization, it's now known that the Palpatine seen in the movie was a clone, and one of many. Thus, Rey's father, who's shown briefly in a flashback, is not a direct descendant of Palpatine, but instead a Palpatine clone with a different face. So while Rey is referred to as his granddaughter, her true connection to the Emperor is a lot more unnatural.
As the theory points out, the multiple versions of Rey could be hints toward her cloning heritage, as multiple versions of Palpatine have likely existed in the galaxy. And even the two shadowy figures merging into one could be seen as a nod towards the dyad in the Force, as she and Kylo are an incredibly unique phenomenon with a strong connection.
While the sequel trilogy receives many complaints about its lack of over-arching story, it's still satisfying to go back and find possible foreshadowing. Additionally, many hope that the idea of Palpatine clones is expanded upon in future Star Wars shows or movies, as much is still unknown.