Doing It for the Art: The amount of work put into this series really shows how much the crew cared about it, even just observing from the surface. But when you start noticing and then paying attention to such trivial things like posters on the walls of clone barracks or clubs, the elaborate details on spaceships, bugs crawling around on branches, garbage thrown away on the lower streets of Corruscant, and dosens of other tiny-little back-ground details, the creators have sneaked in, despite the fact that most viewers probably wouldn't register any of it, it becomes mind-blowing! Then consider that all of this is made in CGI, with a relatively low-budget...
Limited Special Collector's Ultimate Edition: All the individuals Season's DVD and Blu-ray releases contained massive amounts of bonus content, but the Seasons 1-5 Collector's Edition took it even further: it includes the entire series, hours of bonus contents, an episode guide, and the 54-page artbook. And it costs just slightly above the half of the combined cost of the individual Season releases.
Missing Episode: The Clovis arc planned for the fifth season never made it to air.
Never Trust a Trailer: In the trailer for the Season 5 finale, the colour of Anakin's second lightsaber was changed to green so that viewers wouldn't be as likely to suspect that Barriss was behind the Temple bombing.
Official Fan-Submitted Content: The lightsaber technique "Whirlwind of Destiny" used by Petro in "A Test of Strength" was created by nine-year-old Brendon Lake for Hasbro's "Join the Jedi" contest.
The Other Darrin: All characters from the live-action Star Wars movies are voiced by different actors in the Clone Wars series, except for the following ones:
Anthony Daniels returned as C-3PO,
After a few episodes with B.J. Hughes voicing Jar Jar, Ahmed Best returned to the role of the clumsy gungan.
Matthew Wood as General Grievous.
Liam Neeson and Pernilla August reprised their roles as Qui-Gonn Jinn and Shmi Skywalker in "Overlords".
Daniel Logan as Boba Fett and the clone cadets (aside from one who was voiced by Dee Bradley Baker).
Samuel L. Jackson and Christopher Lee reprised their roles as Windu and Dooku respectively in the Pilotmovie before being replaced in the series itself.
After the passing of Ian Abercrombie, Tim Curry takes over as the voice of Chancellor Palpatine.
The Other Marty: When the the three original episodes were edited and released as a feature film, Christopher Lee returned to voice Count Dooku. Corey Burton, who plays Dooku in the ongoing series, had already recorded his lines and Lee re-recorded them, matching his performance to the already-rendered images.
James Arnold Taylor is voicing Obi-Wan, Plo Koon, Osi Sobeck and Rako Hardeen ( both the real one, and while Obi-Wan was posing as him). Hilariously lampshaded in "Counterattack", after Osi Sobeck captured Obi-Wan and his group:
Corey Burton voices Cad Bane, Count Dooku and Ziro the Hutt. Narrowly averted between Ziro and Dooku, as while the two of them are both played by Corey Burton in the series, they conversed with each other only in The Movie, in which Christopher Lee returned to play his role as Dooku.
This does happen, however, in "Hostage Crisis" when Cad Bane and Ziro converse after the latter is rescued by the former.
Matthew Wood voices General Griveous and his battle droids.
Daniel Logan voices Boba Fett and the teenage clone cadets.
Robin Atkin Downes played two minor characters in "Supply Lines": Jedi Master Ima-Gun Di and Cham Sindulla.
Trolling Creator: At the end of "A Necessary Bond", Huyang mentioned that the last Jedi youngling who had such an adventure while building his lightsaber was Yoda. Hearing this the younglings immediately started to demand the story, just for Obi-Wan to quickly put them down, telling them that's Another Story for Another Time.
ARC trooper Alpha-17 was going to be a character in the show until George Lucas nixed the idea because it would mean having too many names beginning with A. As a result, we got Rex, who's similar to Alpha, but with a different name.
Plo Koon was originally going to speak only in his Kel Dor language, but it posed problems for him communicating with his fellow troopers, so they decided to have him speak in Basic (the English language of Star Wars).
Mace Windu and Boba Fett's talk in the end of "Lethal Trackdown" was going to be longer, but had to be cut for time, hence why it feels incredibly rushed.
Darth Bane and Revan were to appear in "Ghosts of Mortis", even getting all the way to modeling, but were cut because them appearing as force ghosts seemed counterintuitive to the now established means for how a force user can appear as one.
Originally, at the end of "Carnage of Krell", Captain Rex was originally going to be the one to kill the traitorous General Pong Krell, but ultimately, they decided it didn't fit Rex, so they ultimately had Dogma be the one to pull the trigger.
For a short while the season five finale was intended to end with Ahsoka just going back to the order as if nothing happened but the majority of the writers felt it would be a good time to break away.
Filoni revealed quite a few of these during the 2013 Star Wars Celebration Europe 2:
There was story-line planned that would've tied the series into the events of Revenge of the Sith. However it was rejected by Lucas, before the cancellation.
There would've been a Yoda-Wookies-arc, had the series not been canceled.
A Sith Temple was to appear in a Yoda-arc.
Mark Hamill also admitted on CE 2, that he had recorded a role for the series. Ironicly, he played a Sith Lord! Sadly, with the series canceled, he's not sure, whether the episode will be finished and included in the "Bonus Content"
The Season 1 episode, The Lair of Grievous, was produced by famous anime studio, Production I.G. The episode won Golden Reel Award, for best sound editing in television animation.
The title logo at the beggining of "Brothers" and "Revenge" was changed to red, as an homeage to Darth Maul's return.
Similarly, the D-Squad arc episodes had blue logo as an homeage to R2.
Kevin Kiner had flown to Prague and hired a full chez orchestra for the recording of the soundtrack of the four-part Season 5 finale arc, and he did it on his own time, out of his own wallet.
"The Wrong Jedi" is the only episode which ends with a Fade Out, and without the usual ending theme. The latter is replaced by Ahsoka's theme, played by the aformentioned full orchestra.
The series won two Daytime Emmy Awards in 2013:
Outstanding Special Class Animated Program
David Tennant won "Outstanding Performer in an Animated Program" for his role as Professor Huyang.