Back in September, AMC announced plans for a spin-off of The Walking Dead that expands this zombie-filled universe with an entirely new story and cast of characters. We also reported in November that the untitled spin-off may be a prequel, set during the early days of the zombie invasion, although that has not been confirmed. Over the weekend, AMC programming head Joel Stillerman spoke about the show, which is still in early stages of development.

"That show is not as far along. Robert (Kirkman) has some things on his plate. He continues to write every issue of the comic and hasn't finished Season 4 of The Walking Dead, which he is very intimately involved with and will continue to be. That's really in the incubation stages. The one thing that I'll share is just an anecdote that Robert shared with us. He has such a specific vision that he laid out really clearly in the first issue of the comic book. And I encourage anybody who's interested in the show to go read the note that he wrote in the first issue of the comic. His motivation for telling that story was so clear and so powerful, and it served as such a great north star for the show. We kicked around a few ideas, but primarily what he's working on is, what is the idea that gives [him] as clear a mandate to make another version of this show as [he] had for the first one? What is going on [now] is a more philosophical discussion over why there should be another version of the show. Once we answer that, we'll zero in on the specific creative.

It's not 100 percent green-lit yet."

AMC network chief Charlie Collier also revealed that they don't want to take anything away from The Walking Dead with the spin-off.

"What we want to do is not diminish the mothership. What we want to do is find something that everyone involved feels as passionately about as being a unique vehicle and unique enterprise as compared to the original series. We'll take our time, and we'll do it right."

They also spoke about the Breaking Bad spin-off Better Call Saul, which AMC announced at their TCA Winter Tour panel will debut in November. Here's what Joel Stillerman had to say about Better Call Saul, which is farther along in development than The Walking Dead spin-off.

Both are in the very, very early stages. Saul is actually a little farther along. That show is committed and on the books now. The writers' room is open. Broad strokes - probably no news here: It is a prequel, it explores what went into shaping the incredibly compelling and idiosyncratic and funny and somewhat tragic character of Saul Goodman. I think the other thing that's really great about Saul: Vince Gilligan and Peter Gould, who are partners on the show, talk a lot about really reinventing the tone of what it means to be a drama. There have been a number of dramas on the air that have had comedic elements. But I think they really want to push the envelope in terms of what it means to take you on an emotional roller coaster ride, and make you laugh, and break your heart and stretch the boundaries of where you can go emotionally within the context of a drama. Saul's obviously a very funny character, and there's going to be a lot of comedy in that show. But they felt at the end of the day that it was best crafted as a drama, and that would give them the latitude storytelling-wise and character-wise to really go into a sort of unprecedented range of emotions."

Charlie Collier said that Vince Gilligan and Peter Gould are going back to the drawing board with the spin-off.

"They're not just [creating] a spinoff. I hate the connotation, because they are really trying to create something original out of a great character. It's so much more than a spinoff. When you hear them talk about it, they really are going back to the drawing board taking the time to invent something."