At one point during the production of Star Wars: The Rise of Skywalker, there were rumors that former Doctor Who star Matt Smith had been cast in the film. But ultimately, he ended up not appearing at all. There have been questions since then about the nature of his supposed role or if he was really going to be involved at all. Now, we have the answers.
Per The Wrap, during an interview in Josh Horowitz's Happy Sad Confused podcast, Matt Smith finally addressed his casting rumor in Star Wars: The Rise of Skywalker. “We were close to me being in it, but then it just never quite happened," he said. As it turns out, he took multiple meetings to discuss his role in the film, but he never got to shoot any scenes or even went to a costume fitting. He did however learn the details of his role which would have been big.
When asked about the details of his supposed role, the actor played coy. He said, "I could not possibly say. I could not possibly say, but it was a pretty groovy thing. Like, it was a really groovy part and concept. It was a big thing. Pretty big — it was like a big story detail, like a transformative Star Wars story detail. But it never quite got over the line." He also added that it would have been a big shift in the history of the franchise.
There have been speculations that the role that Smith might be playing is Palpatine's son, which is possibly why the actor indicated it as a "transformative" role. The way the film handled Palpatine and Rey's familial connection to him has been divisive among fans. This actually proves that there were a lot of script changes during pre-production and they were trying to figure out ways to resolve the conflicts that they set up in the previous two films.
An easy guess is that Smith's role could have been an antagonist that has a connection with Rey's heritage. Maybe he was supposed to be the main villain, instead of having Ian McDiarmid back as Palpatine. We will never know. It is a question that fans will keep on thinking about for a long time. It would have been great to see Smith in the franchise, but perhaps he might be considered again in the future since there are many Star Wars projects that are in the works right now.