The Mandalorian & Grogu is clear with its intention. At no point does it pretend to be anything other than a continuation of the hit show, sending its titular duo on a mission that tests their bond. However, as is par the course with Star Wars movies, a few characters show up that have connections to other projects. The most notable this time around is Zeb Orrelios, a former member of the Ghost crew from Star Wars Rebels.
Unlike his friends Ahsoka Tano, Hera Syndulla, and Sabine Wren, Zeb isn't wrapped up in getting Ezra Bridger back home safe and sound. He's fighting the remnants of the Empire for the New Republic, and Colonel Ward decides he's the right guy to serve as Din Djarin's handler. The unlikely allies destroy an Imperial base at the start of The Mandalorian & Grogu before returning to their headquarters and picking up another assignment: rescuing Rotta the Hutt.
While Din takes the lead because of his connections to the criminal underworld, Zeb is always nearby, ready to provide aid when lasers start flying. The Lasat is such a devoted friend, in fact, that he travels to Nal Hutta with a squad of X-Wings and Y-Wings at the end of the movie to save the titular duo from an army of droids. But at no point during The Mandalorian & Grogu does Zeb get to talk about himself or, more importantly, his friends with unfinished stories.
The main characters in Star Wars Rebels came up against their fair share of nasty Imperials, including Grand Admiral Thrawn himself. One foe that really got under Zeb's skin was ISB agent Alexsandr Kallus, who made a career out of tormenting Lasats. After spending so much time as rivals, though, they came to understand one another. Zeb even offered Kallus a spot in the Rebellion.
At first, Kallus tore down Zeb's olive branch, not wanting to endure the Empire's wrath. However, he soon became disillusioned with his mission and began acting as a spy under the codename "Fulcrum." Of course, more than a few Star Wars characters have used that title, including Cassian Andor, Ahsoka, and Anakin Skywalker. And Kallus was as impressive as any of them, feeding important information to the rebels and helping bring down the Empire from the inside.
Rebels revealed that, after the war, both Kallus and Zeb retired to Lira San, the Lasat homeworld. Kallus was embraced by everyone and looked primed to forge a new life for himself. The only issue with that idea is that The Mandalorian & Grogu makes it clear that Kallus and everyone else didn't finish the job.
Zeb is still out there fighting, so it's fair to assume that Kallus is doing the same, not wanting his former employer to take back power. Unfortunately, The Mandalorian & Grogu doesn't tease Kallus' whereabouts. He doesn't even appear in the bar that's crawling with notable faces in the New Republic.
The easy explanation is that Lucasfilm didn't want to add unnecessary exposition and characters to its latest movie. After all, it can't make sure that everyone who heads to a theater to watch it has seen Star Wars Rebels. But that argument doesn't seem to affect Embo, who makes his live-action debut in The Mandalorian & Grogu after spending his whole career in animation.
Fortunately, a piece of supplementary material reveals that Kallus still has more to give a galaxy far, far away.
Kallus' Star Wars Future Is Tied To His Own Words
Back when TV wasn't an option for Lucasfilm, books were the primary way the studio got information out. While all of the Extended Universe was struck from canon following the Disney merger, the House of Mouse has brought Star Wars books back in a big way.
One particulary interested book by Chris Kempshall, titled Star Wars: The Rise and Fall of the Galactic Empire, revealed that Kallus wrote a memoir about his time working for the Empire called Honor Lost on Lasan: Serving the Empire, Fighting for the Alliance. In it, he described his experience working for both sides and explored his guilt about hurting the Lasat people.
Using the Star Wars timeline as a guide, Kallus wrote the memoir a few years before The Mandalorian & Grogu takes place. So, there's a chance he's still on Lasat, trying to create material to educate the galaxy about the dangers of evil. It would be a noble end for a character who once tried to destroy history wherever he went.
But it's up to Lucasfilm to put a final bow on Kallus' story. Maybe it's something as small as putting one of his books on a shelf in a future season of The Mandalorian or a movie like Star Wars: Starfighter, or it could be giving him the live-action appearance that he's been patiently waiting for and providing him with one last team-up with Zeb.