Did any storylines or content from The Clone Wars exist prior to its broadcasting?

Question

I recently rewatched Attack of the Clones (AotC) and decided to give the The Clone Wars (TCW) animated series a shot before revisiting Revenge of the Sith (RotS) to fill in the blanks between the two films. I'm aware that both AotC and RotS were released before TCW, with the show following the latter by at least 3 years. The show of course portrays a lot of self-contained plots that don't see the light of day outside the show and, for the most part, ultimately don't need to. I've only recently caught up to season 6.

One such element is Ahsoka Tano. In the S5 finale Ahsoka,

Anakin's friend and Padawan, is excommunicated from the Jedi Order (and later given the opportunity to rejoin)

and I feel compelled to emphasize friend here, despite what the Order has to say about forming attachments.

Some sources I've found say Ahsoka did not exist during RotS development. Wikipedia cites a fan interview referring to Ahsoka as a brand new character; this ScreenRant article agrees, but seems to allude to a potential cameo in RotS (admittedly, I did my best to skim the article to avoid spoilers so maybe I misunderstood). This status likely applies to any character not mentioned before in any other Star Wars (SW) media. While the film focuses on the Council's refusal to grant him a seat as one of the final straws,

kicking out his Padawan

seems to me another strong reason to reinforce his mounting distrust and make him feel/act out the way he does.

Given the TCW screen time of such prominent characters as Ahsoka and some of the 501st members, their involvement in important skirmishes or invasions, their multiple brushes with death, and their close relationships to some of the characters of the flagship films, I wonder did there exist any semblance whatsoever of these characters and events prior to the release of RotS? If so, were the main cast (i.e. those playing the roles of Anakin, Obi-Wan, Dooku, Palpatine, Padme, other Council members or senators or bounty hunters with significant screen time, etc.) apprised of the general events of TCW? Were they at all aware of the then-future plans for SW media?

Here's a cooked up example of what I'm looking for: Perhaps during RotS shoots, Lucas hinted to Christensen at the existence and fate of a nameless Padawan or someone else very close to Anakin (besides Shmi and Padme) that is torn from the character, and directed that that help inform his character's growing animosity towards the Jedi authority, to supplement the emotional turmoil the audience witnesses on screen. The actor need not know the Padawan's name, just that his character had a Padawan.

Perhaps the answer is as simple as, "No, everything you see in TCW is new and was retrofitted to be more or less consistent with what the previous films and other media had already established." It would be nice to see an official statement or interview that either confirms one way or the other.

Answer 1

According to starwars.com Ahsoka and all the other Clone Wars original characters weren't invented until the development of the show began after Dave Filoni was hired by Lucasfilm in 2005, after Revenge of the Sith was already in post-production.

It’s hard to imagine now, but Star Wars: The Clone Wars almost wasn’t a story about Anakin Skywalker and his Padawan, Ahsoka Tano. Supervising Director Dave Filoni’s original vision for the series, scribbled on a piece of lined paper, involved a band of misfit scoundrels aboard a freighter and operating on the fringes of the galactic conflict. It would have included a Padawan Learner named Ashla, and her Jedi Master on assignment with the crew, working to aid the war effort by dealing with arms dealers and crime bosses like the Hutt clan. It would have occasionally brought the pair back to the frontlines to defend the Republic.

So characters and plotlines from the show could not have been alluded to or told to the cast as reference since they were created during pre-production of the show.

Answer 2

Honestly it was kind of hard to know exactly what you were asking. But this question is also hard to answer because all I could think of was Ahsoka. I mean what else was created entirely for the Clone Wars show, that possibly had a chance of being shown prior? I was going to mention the 2D Mini-Series that came out in 2003, but I don't think that mentions anything specific to CW.

There is the reveal of Darth Maul still being alive, so I checked his Wikipedia page and it made me realise how easily this question could be answered: comic books.

They always get made before any films or shows, and the concepts in them are always more advanced than the other mediums. And wouldn't you have it, there was in fact a comic talking about a CW storyline.

Star Wars: Visionaries is a 2005 collection of 11 stories based across varying time periods in the Star Wars universe. One story, "Old Wounds", mentions a hooded Force-user with cybernetic legs on Tatooine, threatening to harm a young Luke Skywalker. Obi-Wan is hiding nearby, and talks to him with the Force. Eventually, Obi-Wan jumps out from his hiding spot, and then the dark figure takes off his hood and reveals himself as Darth Maul, with his horns having grown to triple their size. This is very similar to what was shown in Clone Wars, although reading it also reminds me of an episode in Star Wars: Rebels.

That's all I can find for now, but that should answer your question.