Captain Rex is based on Dark Horse comics ARC Trooper Alpha. But on realizing there were already three other characters who's name started with A (Anakin, Artoo and Ahsoka), George Lucas proposed the name 'Rex' instead.
In order to make the Clone Troopers sound like individuals, Dee Bradley Baker recorded every voice separately and gave each one a different inflection. He liked to write down a particular adjective for each one. For instance some sound a bit younger, others a bit more proper whereas another may sound like a bully or a grunt. During later seasons, he was able to record all the voices in the same take.
Dave Filoni based the character of Ahsoka Tano on the mannerisms Carrie Fisher displayed as Princess Leia in the original Star Wars trilogy. Further more, she combines Anakin's brashness with Obi-Wan's measured judgment, reflecting the shift between the Republic and the oncoming Empire.
The series is presented as an anthology, meaning the stories are not shown in a strict chronological order but can jump around in the time-line. This is much like George Lucas previous television series The Young Indiana Jones Chronicles (1992).
The series started the same year that the video game Star Wars: The Force Unleashed (2008) was released. Both this series and the game introduced an apprentice (Ashoka in the series and Starkiller in the game) to Anakin/Darth Vader. Both apprentices hold their lightsabers in the Shien reverse grip. The year Star Wars: The Force Unleashed II (2010) was released both Starkiller's clone and Ashoka began duel wielding lightsabers. Sam Witwer voiced both Darth Maul on this series and Starkiller in the games, who also share several similarities.
It is an unwritten rule in films to have the good guys move from left to right and the bad guys right to left during battle scenes. The Clone Wars series, like Star Wars: Episode II - Attack of the Clones (2002) before it, shows the Republic Forces (the good guys) moving from left to right. This foreshadows the Clone Army becoming the Imperial army (the bad guys).
When Matt Lanter auditioned for the part of Anakin Skywalker, he was told he was up for the part of "Deak Starkiller". Director Dave Filoni and producer Catherine Winder then told him to play a combination of Han Solo and Luke Skywalker.
Dave Filoni and first season head writer Henry Gilroy had originally assumed that Obi-Wan and Anakin would only make occasional appearances on the show because most of their Clone Wars activities had already been told in printed work and in Star Wars: Clone Wars (2003). Instead, the main characters were to be a Twi'lek Jedi called Sendak and his Togruta apprentice Ashla (later to become Ahsoka) who fought piracy and mercenaries around the galaxy. They would team up with a Han Solo like smuggler called Cad, his mistress Lupé and their Gungan strongman Lunker. Another idea was to stick to a couple of recurring locations, not unlike the TV show Firefly (2002) and keep landscapes to a minimum for rendering and conceptualization reasons. However, they soon found out that George Lucas didn't intend to keep The Clone Wars small.