'The Walking Dead' Season 4: Sonequa Martin-Green on Sasha and Tyreese's new roles

Fans of Tyreese and Sasha on "The Walking Dead" should start getting really excited about the upcoming Season 4, because both characters get to come to the forefront much more this year than they did last. Sonequa Martin-Green spoke to Zap2it at "The Walking Dead's" premiere red carpet about what viewers can expect to see of Sasha and the rest of the Prison's new residents.

"I think at the very end of Season 3, they became a part of the group, as well as everyone else from Woodbury," she says. "I think that everybody made a collective decision to just move forward together, and it was because of Rick. It was because he made the decision and it trickled down from him. Yeah, [Sasha and Tyreese are] definitely in the group. They're integral in the group. They're helping. They're in leadership positions."

Martin-Green says she was thrilled to have her involvement with the rest of the group increased because it led to her having some awesome zombie kills. "My favorite is one that happens in the first episode. It's one of mine," she says. "I won't give it away, but it's great and I thank [director] Greg [Nicotero] for it."

There's been a lot of vague discussions of a new threat facing the survivors in "The Walking Dead" Season 4, though there hasn't been any clear explanation of what it is. While Martin-Green didn't reveal the latest trouble Rick & Co. will have to face, she did say that it's a gamechanger.

"It turns the whole world upside down because it's something you never would have expected. It's shocking," she teases. "I was shocked when I first read these scripts. I said, 'What?' It's going to be great."

Martin-Green admits that Hershel is her favorite person on "The Walking Dead," but in Season 4 people should keep an eye out for Alanna Masterson's mysterious new character. "Keep an eye out for her right here. For real," Martin-Green teases.

"The Walking Dead" Season 4 premieres on Oct. 13 at 9 p.m. ET on AMC.

Photo/Video credit: Zap2it/AMC