Captain Rex of Star Wars: The Clone Wars and Star Wars Rebels may not be the soldier Star Wars: Episode VI - Return of the Jedi after all. As part of the well-trained Clone Army in The Clone Wars, Captain Rex was a great companion to the Jedi until Order 66 was executed. But while most of his comrades blindly followed the Imperial orders of hunting down the Jedi, he was one of the few who quickly figured out that they were part of an evil plot and went into exile. His initial appearance on Star Wars Rebels and first contact with the Ghost Crew - especially with Kanan - was still filled with tension and distrust coming from both sides, seeing as the last time Kanan saw clones, they were shooting at him. The two eventually patched things up and since then, the Clone Trooper has helped the budding Rebellion in their mission to save the galaxy from the clutches of the Galactic Empire.
While the Clone Troopers became pivotal story players in The Clone Wars and was later revisited in Rebels with the introduction of Captain Rex, not much is known as to what happened to them during the events of the original trilogy, so when Steven Melching, a writer for Star Wars Rebels seemingly tweeted a confirmation that Rex could have appeared in Return of the Jedi, fans were naturally thrilled of the connection as some sort of Easter egg. Unfortunately, Melching has now walked back his previous comments and clarified his original intent.
Taking to Twitter, Melching penned a series of tweets explaining that he did not mean for his previous "confirmation" to serve as any sort of official reveal that Rex and a soldier known in the former Expanded Universe as Nik Sant - a Rebel commander from the attack on the shield generator station in the Battle of Endor - are the same person:
"Friends, please allow me to clarify my provocative and badly-worded tweet from earlier today. 1/....When Rex was redesigned for his appearance in S2 of REBELS, many people saw a similarity to “Nik Sant” in ROTJ. 2/.... I didn’t notice the resemblance until fans pointed it out after the release of the S2 trailer. 3/...Many on the crew found the resemblance amusing too, but AFAIK it was not an intentional design choice. 4/...In each season most character models change. As the Ghost crew grows closer to the larger Rebellion, their costumes often reflect that. 5/...Rex is clearly wearing some costume pieces that resemble the Rebel Commandos from ROTJ. As a soldier, this makes sense. 6/ So are Rex and Nik Sant one-and-the-same? Truthfully, I do not know the answer. I wish I had made that clear originally. 7/"
While Melching might not have that answer, it's one that Executive Producer Dave Filoni has supported on several occasions, so even though Melching is walking back his earlier "confirmation," there's still a good chance that Nik Sant will have been Rex all along.
This is not the first time that fans believed that a Rebels character may have appeared in one of the live-action films purely based on aesthetics. Last year, there were some speculations that Agent Kallus was actually in Rogue One: A Star Wars Story as one of the Rebel commanders that interrogated Jyn and ordered Cassian to assassinate Galen Erso. The theory was specifically popular at that time as it also coincided with Kallus' big story arc in Rebels season 3 that ended with him switching sides from the Empire to the Rebellion. This was, however, eventually debunked as the real name of the anthology film character was revealed to be Davits Draven.
Source: Steven Melching