Deschanel soon became known for her deadpan comedy roles in films such as The Good Girl (2002), The New Guy (2002), Elf (2003), The Hitchhiker's Guide to the Galaxy (2005), Failure to Launch (2006), Yes Man (2008), and (500) Days of Summer (2009).
The New York Times found Deschanel to be "particularly spontaneous, unaffected and emotionally direct" in her role. In the comedy Big Trouble, with Tim Allen and Rene Russo, she played the daughter of Russo's character, and she starred in the teen comedy The New Guy as a guitar player in a band.She took on the role of a cynical, plain-spoken young woman working in a big-box store in the black dramedy The Good Girl, starring Jennifer Aniston and Jake Gyllenhaal.Deschanel next appeared in Failure to Launch (2006), as the neurotic roommate of Sarah Jessica Parker's character.She also had a recurring role in four episodes of the Showtime television series Weeds from 2006 to 2007 where she played Kat, Andy Botwin's quirky ex-girlfriend.Her performance received critical praise, In 2004, Deschanel starred in Eulogy and in 2005, she played Trillian in the film adaptation of Douglas Adams' science fiction novel The Hitchhiker's Guide to the Galaxy.
She acted in Winter Passing (2005), co-starring Will Ferrell.
Despite largely negative reviews, critic Roger Ebert felt that Wahlberg and Deschanel's performances "bring a quiet dignity to their characters", She starred in the independent comedy Gigantic (2008), which screened at the Toronto International Film Festival and was distributed for a limited release in certain parts of the United States only.
In the comedy Yes Man (also 2008), she played an unorthodox singer and the girlfriend of Jim Carrey's character.
Her paternal grandfather was French, from Oullins, Rhône; her roots also include Swiss, Dutch, English, Irish, and other French ancestry.
Deschanel lived in Los Angeles, but spent much of her childhood traveling because her father shot films on location; she later said that she "hated all the traveling ...
I'm really happy now that I had the experience, but at the time I was just so miserable to have to leave my friends in Los Angeles and go to places where they didn't have any food I liked or things I was used to." Deschanel had a guest appearance on the television series Veronica's Closet in 1998 and made her film debut in Lawrence Kasdan's comedy Mumford (1999), revolving around the neurotic residents in a small town and co-starring Hope Davis, Jason Lee, Alfre Woodard and Mary Mc Donnell.