Also nominated for best original screenplay were Judd Apatow for "Knocked Up," another comedy about an unplanned pregnancy; Tamara Jenkins for "The Savages," about adult siblings caring for their ailing father, and Nancy Oliver for "Lars and the Real Girl," in which a loner falls for a life-size doll.
Many of the year's most acclaimed films were based on books, making the adapted screenplay category especially competitive. The nominees include Joel and Ethan Coen's adaptation of Cormac McCarthy's Texas crime novel, "No Country for Old Men," and Paul Thomas Anderson's loose adaptation of Upton Sinclair's novel "Oil!" - which he turned into "There Will Be Blood."
Also nominated for best adapted screenplay were Sean Penn's script for "Into the Wild," based on Jon Krakauer's book, Ronald Harwood's adaptation of Jean-Dominique Bauby's memoir "The Diving Bell and the Butterfly," and James Vanderbilt's script for "Zodiac," adapted from Robert Graysmith's book about San Francisco's Zodiac killer.
Nominees for the third and final category, documentary screenplay, were Michael Moore's script for "Sicko," as well as those for "Nanking," "No End in Sight," "Taxi to the Dark Side," "The Rape of Europa" and "The Camden 28."
The Writers Guild Awards winners will be announced Feb. 9. The Los Angeles-based West division of the WGA said it will not host an awards show until the strike is over. The New York-based East division of the guild said it has not yet decided whether it will have a ceremony.
The guild's strike is causing considerable turmoil this awards season. On Monday, organizers facing the prospect of a Golden Globes ceremony without any celebrities - who said they wouldn't cross picket lines - reduced the event to a news conference.
