Dave Filoni admitted that one condition Sarah Michelle Gellar had before joining the show was that Kanan, played by her husband Freddie Prinze, Jr., wouldn't be the one to kill her. Therefore, the Seventh Sister's death came at the hands of Maul.
According to Freddie Prinze Jr., the voice actors were told that something would happen in the last couple of minutes of "Twilight of the Apprentice", but nothing was known of it due to it being a dialogue-less scene.
In a Collider Jedi Council podcast and a couple of other interviews with Freddie, the voice actors already know what will happen to their characters, only waiting for how their stories will be executed (as in, they don't know the exact events that will lead up to those milestones until they receive the episode scripts). In a First Order Transmission interview, he even reveals that he knew as early back in the recording of Season 1 that Kanan would become blind at some point, but didn't know who would inflict it.
Sam Witwer revealed that he and Ashley Eckstein were given a rundown on what happened to their respective characters up to Revenge of the Sith.
It seems that the voice actors for the Inquisitors are not informed on what their characters have done and their future, but the writers on the other hand seem to know, as Jason Isaacs did not seem to be aware that the Grand Inquisitor was a former Jedi Temple Guard until he recorded for it, and Philip Anthony-Rodriguez was only informed that the Fifth Brother was European/Spanish-based and blind, nothing beyond that.
An IGN interview with Filoni after "ZeroHour" revealed that Kallus' story arc was planned from the start.
One of the writers has mentioned on a post-Season 1 finale interview that the show is structured by 3 acts, with Season 1 being Act 1, as well as that not all the acts will necessarily correspond to each season. Act 2 also begins with Season 2, but will not end with its season finale.
Adding to the above example and an entry below in Word of Saint Paul, Pablo Hidalgo has implied that the show will move past Season 3 as well.
Filoni clarifies a bit of what happened on Malachor. He also says that he had a name in mind for the voice that came out of the Malachor Sith Temple.
It has been said that a Mandalorian relations chart has been created by the writers for reference.
In "Imperial Supercommandos", when Rau describes Saxon as being 'part of Clan Vizsla, like [Sabine]', Hidalgo tweeted that the script should have said he was of House Vizsla and not actually from the clan itself.
Greg Weisman had stated interest in doing a spin-off Hera Syndulla comic similar to Marvel's Kanan. and expressed it to Disney.
As the members of Iron Squadron have names based off of John Harper (cameraman for The Star Wars Show), Andi Gutierrez (host of The Star Wars Show and Rebels Recon), and Matt Martin (member of the Lucasfilm Story Group), they recorded temp dialogue for the titular episode.
Before the airing of Season 2, Filoni had said that he wanted to do an episode that took place from the perspective of the Empire, but it wasn't supported enough by the other writers to do in Season 2. Instead, "The Honorable Ones" focused on Kallus away from the Empire, and eventually, we got "Through Imperial Eyes", which gave some insight on the inner workings of the Empire through the eyes of a rebel spy.
During the Season 3 to Season 4 hiatus, Filoni stated he always personally believed Kallus's first name is Alexsandr. This fact never comes up on the show at all.
Right after the Grand Finale aired, Filoni noted that while he wouldn't reveal what exactly happened to Ezra and Thrawn at the end, he did confirm that both characters survived, or at least as he would have it.
, he even reveals that he knew as early back in the recording of Season 1 that Kanan would become blind at some point, but didn't know who would inflict it.