Star Wars: The Rise of Skywalker gave Rey what Mark Hamill always wanted for Luke Skywalker. As the respective protagonists of the sequel and original trilogies, there are numerous obvious parallels between the two characters. Chief among them is they are both descendants of dark side users. Luke's father, of course, is Darth Vader, while Rey is Emperor Palpatine's granddaughter. That lineage played an integral role in Luke and Rey's arcs, as they tried to resist the temptation of the dark side and stay on the path of the light.
Neither hero ultimately turned to the dark side, but there were moments when their fate was in question. In particular, part of Rey's journey in The Rise of Skywalker is learning to not be afraid of who she is. Even before discovering her true nature as a Palpatine, Rey has visions of her sitting on the Sith throne. Audiences got a brief glimpse of what this outcome would have looked like with The Rise of Skywalker's Dark Rey scene. It was an interesting "what if?" scenario, and in a way, it's something Hamill had envisioned for Luke years ago.
When George Lucas and company were gearing up to make Return of the Jedi, Hamill was anticipating Luke going to the dark side. Considering the character's all-black costume, the actor figured that's where the story was going, but he was wrong - much to his chagrin. As he said in an interview, "Every actor wants to play their own evil twin."
While Rey didn't actually turn to the dark side and become Empress Palpatine, Daisy Ridley did get an opportunity to play her evil twin in a short sequence where Rey crosses paths with Dark Rey and the two have a skirmish. The likelihood J.J. Abrams and Chris Terrio were intentionally referencing Hamill's old wishes are low, but it still makes for a fun parallel - especially for those familiar with what Hamill wanted for Return of the Jedi. Watching the scene, it might make one wonder how Hamill would have played evil Luke if that's where Return of the Jedi decided to go.
As interesting as it was to see Dark Rey, the concept's integration into The Rise of Skywalker could be perceived as disappointing. Particularly after Dark Rey was seen at the end of a Rise of Skywalker trailer, there were numerous theories speculating on what it could mean and the impact Dark Rey may have on the story. For Dark Rey to ultimately be in The Rise of Skywalker for a few fleeting moments was arguably a letdown. Still, it was fun while it lasted in the movie and allowed Ridley to channel a different side audiences didn't see much of in the sequel trilogy. And now, she can always say she got to live Hamill's dream in her own way.