Contest Winner Cameo: Of a sort. Cartoon Network ran a poll to choose which of three new Jedi would appear in the second season finale: Shistavanen Wolf Man Voolvif Monn, yeti-like Talz Foul Moudama, or Ithorian Roron Corobb. Voolvif won, but the other two showed up in the third season with larger roles than his. And then got killed by Grievous.
Uncancelled: Well, more like Un-ended. The micro series was only meant to last two seasons and there were no intentions for a third. But due to positive fan response, Lucas commissioned one more season to help lead into Revenge of the Sith.
What Could Have Been: General Grievous was never planned to appear in the micro series. Durge was going to have his story arc ended in Chapter 20, but George Lucas thought it would be better to introduce Grievous a year before Episode III.