Star Wars has more than one Captain Rex, and the original character joined Star Wars canon in 2014. Given how big the Star Wars franchise is - spanning not only movies but also video games, comics, and novels - it's not too surprising to think that there are multiple characters with the same name, especially if one person lived thousands of years before the other. But when it comes to Star Wars in general, fans tend to think of one person when they hear the name, Captain Rex.
Of course, that Captain Rex is Clone trooper CT-7567, who first appeared in the animated film Star Wars: The Clone Wars and later reappeared throughout the entirety of the animated Clone Wars series. After that, rather than be incorporated into the Galactic Empire, Rex fought alongside the Alliance in Star Wars Rebels. For Star Wars animated fans, Captain Rex is one of the most important characters in the franchise, and he actually is that important in the grand scheme of things. But the thing is, he's not the only Captain Rex in Star Wars.
In the Star Wars Rebels season 1 episode, "Droids in Distress", Lucasfilm quickly introduced the droid RX-24, a Star Commuter 2000 pilot who was transporting people from Lothal to the planet Garel. For the uninitiated, RX-24 is originally the StarSpeeder 3000 pilot - voiced by Paul Reubens - seen inside the Star Tours ride in Disneyland's Tomorrowland. He's been nicknamed Captain Rex for several years, long before the Clone Wars' Captain Rex made his first debut in the animated series.
While this certainly can be considered a stretch to some degree, RX-24 was officially brought into canon in 2014 through Star Wars Rebels and then canonized once again when he transformed into a DJ inside Oga's Cantina earlier this year. According to canon lore, Rex crash-landed on the planet Batuu and was ultimately reprogrammed into a DJ by a person named Mubo. And as of 2019, Lucasfilm and Disney made RX-24's nickname somewhat official by renaming him R-3X inside Disneyland's Star Wars: Galaxy's Edge - a Disney Parks themed land that is considered fully canonical in the Star Wars saga.
Sure, R-3X is no longer a pilot in the Star Wars franchise, but that doesn't erase his history. While many people are happy with only the Clone Wars' Captain Rex running around the galaxy, there's no reason Star Wars fans can't have more than one Rex in the universe, even if one of them is now simply entertaining bar patrons with, hopefully, entertaining music.