Recycled Script: Most episodes are either about Jack attempting to find a way home, Aku sending a new assassain to kill Jack or finding a way to do it himself, or Jack finding some group of people oppressed by Aku's regime and helping to free them. It works in this case since the show really is more about fight sequences and strategy than storyline. And toward the end of the show, episode plots started to branch out more, with some new twists on ones that were already established.
Aku: Oh, put that thing away, Samurai. We all know what's going to happen. You'll swing your sword, I'll fly away, and probably say something like, "I'll be back, Samurai!" And then I'll flutter over the horizon and we probably won't see each for... about a week. And then we'll do the same thing again.
Jack: Your word play will not trick me, villain! (Charges)
Aku: (Transforms into a bat, floating away)
I'll be back again, Samurai! You'll see! MWAHAHAHAHA! (Reappears)
See what I mean?