10 Things You Learn Rewatching Star Wars Rebels
7. What Happened To Gregor?
When the Rebels first bring Captain Rex, of Clone Wars fame, they find him alongside two other Clone Wars veterans, Wolfe and Gregor. All three had removed their inhibitor chips before Order 66, with Rex's removal the subject of the final Clone Wars arc, so they spared themselves from the fate of becoming mindless Imperial killing machines when Palpatine triggered Order 66.
Though it's nice to see old friends again, the Gregor seen in Rebels is not the same clone we see in Clone Wars. In his brief story arc on that show, he suffered from amnesia and lived on the planet Afabar. When he meets a Republic team made up entirely of droids, they help jog his memory, and we see him as a brave and stoic soldier before sacrificing his life for the droids and their commander, Colonel Meebur Gascon.
Despite his sacrifice, Gregor appears alive and well (until the finale) in Rebels. Not only that, but he appears to be an entirely different clone. Rather than the serious warrior from Clone Wars, Rebels Gregor treats everything like a joke, and even uses Zeb as bait to catch dinner.
Perhaps, given how out of character he acts and his apparent death in Clone Wars, this is an entirely different clone named Gregor?