UPDATED: "Retired at 35" alum Josh McDermitt will portray Eugene, a former science teacher in the series created by Robert Kirkman, while "Southland's" Michael Cudlitz will play tough-guy Abraham.

AMC's The Walking Dead is bringing in two more pivotal characters from Robert Kirkman's long-running comic series on which it is based.

Retired at 35 alum Josh McDermitt has joined the zombie drama in the series regular role of Dr. Eugene Porter, The Hollywood Reporter has learned. He'll be joined by Southland alum Michael Cudlitz as his traveling companion (and series regular role) Abraham, producers announced Saturday at New York Comic-Con, where the actor was a surprise addition, appearing in character from the audience.

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[Warning: Spoilers from the comics series follow.]

In the Image/Skybound comics, Eugene is a former high school science teacher who first appears in the 53rd issue of the series. He travels with sports coach and Army Sgt. Abraham Ford (Cudlitz) and Rosita (new recurring player Christian Serratos).

The trio eventually crosses paths with Rick as they make their way to Washington. However, unbeknown to Rick as well as eventual couple Abraham and Rosita, Eugene is lying when he claims to know what caused the zombie outbreak and instead is using the physically superior former sports coach to protect him.

The character remains alive in the comics and proves to be a key part of Rick's group, using his science know-how to manufacture ammunition.

"We're going to tell a version of the Eugene, Abraham and Rosita comic stories, that's what we do," showrunner Scott Gimple tells THR, noting that like the series has done before, there will be similarities and differences to how AMC handles the characters. "I love those characters from the book; they are very different flavors of comic book characters than we've seen on the show."

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Eugene for his part, disguises the fact that he's a smart guy by altering his appearance in order to further protect himself. "Josh looks breathtaking in a mullet; he was born to wear one," Gimple said with a laugh. "I can proudly announce we will see a mullet!"

The arrival of the characters also opens the door for the series to explore different locations than the prison. "We're going to get to those characters in a bit, but before that, we're going to be exploring a lot of different locations," Gimple says. "We're at the prison the first two episodes. We start looking at other places in episode three on but that isn't even tied with them yet.

Abraham, meanwhile, is a married father of two who following the outbreak returned from a hunt for supplies to find his wife and young daughter had both been raped and his young son force to watch. He ultimately kills the culprits and loses his family, who flee him in fear and are latter found, turned. He eventually becomes Rick's right-hand man after his group loses a key member in battle.

Repped by Innovative and Trademark Talent, McDermitt's credits also include Work It, Last Comic Standing (where he was a semifinalist during season four) as well as ABC pilot Kings of Van Nuys. He was a regular on TV Land's recently canceled Retired at 35.

Cudlitz is repped by APA, Gold Coast and Stone Meyer. His credits include TNT's recently canceled Southland as well as Band of Brothers.

The Walking Dead returns for its fourth season Sunday at 9 p.m. on AMC. What do you think of the castings? Check out Cudlitz in action as Abraham from season four, below.

E-mail: Lesley.Goldberg@THR.com

Twitter: @Snoodit