'The Walking Dead' gets a 'Good' guy; plus, casting scoop on 'Dexter,' 'Game of Thrones,' 'CSI: NY' and more

Hope you're hungry, because we have a heaping helping of TV Snacks today. Enjoy 'em while they're hot!

Dallas Roberts ("The Good Wife," "Rubicon") is joining "The Walking Dead" as Milton, who, unlike most of the characters inspired by Robert Kirkman's comics, is wholly original to the TV series. "Milton is the details guy," Kirkman tells EW, "[who] works with the Governor...He's not exactly a scientist, but he's a smart guy that is trying to find out how zombies behave. Watching him do his little experiments is going to be a lot of fun." [EW]

Our favorite serial killer reunites with his long-lost stepchildren -- Astor anyway -- in the second half of "Dexter's" Season 7. Christina Robinson, who plays Rita's angsty daughter, was photographed with Michael C. Hall filming a beach scene in Los Angeles. "Dexter" returns to Showtime Sept. 30. [The Insider]

Two more Brits have joined the ever-expanding Season 3 cast of "Game of Thrones": Rapper Ed Skrein will play Daario Naharis, the mercenary captain enlisted by Daenerys Targaryen (Emilia Clarke) to sail into Westeros, and Jacob Anderson (U.K.'s "Episodes" and "Skins") is taking on the role of Grey Worm, leader the Unsullied eunuch slave soldiers. [WinterIsComing.net]

"Justified" scoundrel Neal McDonough is guesting on "CSI: NY" this fall as a good-guy senator who is injured -- along with Lindsay (Anna Belknap) -- in a shootout. [TV Line]

Acclaimed playwright David Mamet ("Glengarry Glen Ross") is rebooting "Have Gun - Will Travel" for CBS. The Western drama, which aired 225 episodes from 1957 to 1963, followed the adventures of "champion-for-hire" gentleman gunfighter (played by Richard Boone). "Gun" is Mamet's second TV project; he created "The Unit," which aired on CBS for four seasons. [Deadline]

Matthew Broderick is lending his voice to the Cartoon Network's "Adventure Time." In the Labor Day episode, titled "Who Would Win," Sarah Jessica Parker's hubby plays the Dream Warrior is a used car salesman summoned by Finn and Jake in a shared dream for advice on besting a rival. "I heard about 'Adventure Time' because my son, James, loves it,' Broderick told the network. "I like that it doesn't talk down to anybody." [Cartoon Network]

"Psych" is boosting its geek IQ with Neil Grayston (Fargo on Syfy's "Eureka" and "Warehouse 13"). In the seventh-season episode titled "The Santabarbarian Candidate," he plays Jason Straub, a sharp political aide for Santa Barbara Mayor Gavin Channing (Sebastian Spence). John Kapelos ("The Breakfast Club") also guests as Tom Swaggerty, a Santa Barbara City Council leader. [USA]