(CNN) For "Star Wars Rebels," the battle is soon going to be over, as the animated Disney XD series forges ahead in its fourth and final season, during what's become an especially busy time in the "Star Wars" galaxy.

The latest two-part episode reflects how the show, set several years prior to the original movie, has gradually run out of real estate, while dipping into other parts of the franchise. It features appearances by the rebel leader Mon Mothma and the character Saw Gerrera, introduced in the prequel "Rogue One: A Star Wars Story." (Forest Whitaker, who played Gerrera, again provides the voice.)

Dave Filoni, the Lucasfilm Animation veteran who has overseen "Rebels" and before that the computer-animated "Clone Wars," said the ending had less to do with the "Star Wars" timeline -- which has grown more crowded with its emphasis on stand-alone features, like the upcoming Han Solo movie -- and more with the program's natural lifespan.

"You wanted to draw conclusions to some of the characters," Filoni said, adding that in terms of the youthful audience that serves as the show's foundation, "If you can keep them for four years, it's actually quite an accomplishment."

The most recent "Clone Wars" premiered in 2008, during a relative drought after George Lucas completed the second movie trilogy. By contrast, "Rebels" made its debut in 2014, following the Walt Disney Co.'s 2012 acquisition of Lucasfilm and an accelerated production pace intended to generate maximum bang for those bucks.

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