Star Wars: Clone Wars, Cartoon Network
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This is an animated micro-series, made up of 25 short episodes over three seasons, set between the live-action Star Wars movies Attack of the Clones and Revenge of the Sith. The first two seasons each consisted of 10 episodes of about three to five minutes each, while the third season consisted of 5 episodes of twelve to fifteen minutes each. The microseries is about the Clone Wars, in which the Galactic Republic fought the Separatists. There was lots of great action, full of butt-kicking Jedi, clones, and droids... familiar characters like Obi-Wan, Anakin, and others, as well as new characters like the awesome Sith apprentice Asajj Ventress, and the also awesome half droid/half alien Separatist, General Grievous (who is later seen in Revenge of the Sith, though I think he's cooler in the cartoon). It was a collaboration between LucasFilm and Cartoon Network, and it was made by Genndy Tartakovsky, creator of Samurai Jack, so hopefully that alone would tell you how cool this show is. Not sure what else to say, but at some point I should rewatch it and see if I can write up a more comprehensive review.
However, several years after the microseries, there came a new full length CGI-animated series called Star Wars: The Clone Wars (note the addition of "The" to the title). I'm pretty sure when the original microseries aired, it was considered canon within the Star Wars universe, though now I'm not sure. I think the CGI series may have negated this one, which would be a shame. But then again, maybe both series can coexist within the canon...