The Clone Wars
There are two Clone Wars Series both of which I believe are incredible and possibly some of the best Star Wars to exist. Both are animated and have rather different styles and have some inconsistencies between the two. If you want something short to watch just watch the Genndy Tartakovsky 2003 Clone Wars series. If you want the full story of what happened throughout the clone wars watch the new Clone Wars series that started in 2008 with a film and then an animated series. Just be wary that these start a little rough and improve a lot later. There are also a few wacky episodes that are probably better skipped. Also, the last 4 episodes of the final season overlap with Revenge of the Sith and should be watched after Revenge of the Sith if you haven't seen it.