Channel Surfing: Lena Headey Crowned for "Thrones," HBO Goes to the Mattresses for "Boardwalk Empire," Pam Gets New Mom on "Office," and More

Welcome to your Wednesday morning television briefing.

The Chicago Tribune's Maureen Ryan is reporting that former Terminator: The Sarah Connor Chronicles star Lena Headey has signed on to star in HBO's fantasy drama pilot Game of Thrones, based on the novel series by George R.R. Martin. Headey, who toplined the now-canceled Terminator, would play Cersei Lannister, described by Ryan as "a woman of royal blood who is every bit as smart, cunning and devious as the powerful men around her." She joins a cast for the pilot (directed by The Visitor's Tom McCarthy) that includes Nikolaj Coster-Waldau, Sean Bean, Peter Dinklage, Mark Addy, Jennifer Ehle, and a slew of others. Headey's character is the sister of Jamie Lannister (Coster-Waldau) and the wife of King Robert (Addy). (Chicago Tribune's The Watcher)

Elsewhere at HBO, the pay cabler has given a series order to period drama Boardwalk Empire from executive producers Martin Scorsese and Terence Winter (who also created the series). Twelve episodes (including the pilot) have been ordered and are expected to air late next year, with production starting this fall in New York. Set in the 1920s, the series follows the life of politico/gangster Nucky Thompson (Steve Buscemi) during the growth of Atlantic City. Buscemi will be joined by Kelly Macdonald, Michael Shannon, Michael Pitt, Shea Whigham, Dabney Coleman, and Stephen Graham. (Variety)

Linda Purl (Bones) has been cast as the mother of Pam Beesley (Jenna Fischer) on NBC's The Office, where she will appear next month at Pam and Jim's wedding. Purl replaces Shannon Cochran, who guest starred as Pam's mom in a Season Two episode of The Office. (Entertainment Weekly's Ausiello Files)

AMC has ordered a fourth season of period drama Mad Men. (Televisionary)

ABC has signed two separate talent holding deals with Martin Henderson (Inside the Box) and Leah Remini (The King of Queens). Under the deals, Henderson will star in a drama pilot for the network, with Henderson meeting with writers shortly to discuss potential properties. Remini, who appeared in ABC's comedy pilot Married Not Dead this past development cycle, will appear in a comedy pilot. (Hollywood Reporter)

Debi Mazar (Entourage) has been cast in a recurring role on ABC's Castle, where she will play Paula Haas, Castle's book agent. Her first appearance is set for October. (Entertainment Weekly's Ausiello Files)

20th Century Fox Television has signed two separate overall deals with Family Guy writers Mark Hentemann and Steve Callaghan. Under the terms of the deals, Hentemann and Callaghan will become executive producers and showrunners on Family Guy (following the decision made by David Goodman and Chris Sheridan to step down as showrunners on the FOX series) and will also develop new projects for the studio. (Variety)

Saturday Night Live will add at least two new female cast members to its roster, hiring The Groundlings' Nasim Pedrad and UCB's Jenny Slate for next season, which kicks off September 26th on NBC. (The Wrap's TV MoJoe)

A. Smith and Co. have acquired the US rights to Japanese game show Pressure Study, in which seven contestants are forced to work together in order to complete seven rounds of questions that will test every facet of their combined knowledge. Series, which will be retitled Under Pressure, is currently being pitched to networks. (Variety)

Stay tuned.