Looking for a change of pace after a long run on “The West Wing,” Allison Janney has joined the cast of the New Line musical “Hairspray” and made a deal to develop a sitcom at CBS. Janney, who won four Emmys for her role as White House chief of staff C.J. Gregg, will start rehearsals on the Adam Shankman-directed “Hairspray” right away. She’ll play Prudy Pingleton, the overbearing mother of Penny (Amanda Bynes) who believes that dancing and having fun is sinful. She joins John Travolta, Queen Latifah, Christopher Walken, Bynes, Michelle Pfeiffer, James Marsden, Zac Efron and Nikki Blonsky. Production on the Leslie Dixon-scripted film begins in September for a summer 2007 release.