Hollywood actress Christina Applegate struggles not to swear while lending her voice for her upcoming film `Alvin and the Chipmunks: The Squeakquel`.The actress, who battled breast cancer in 2008, said she had to make sure she never went off the script at any point during voicing a character in the film where she plays a member of the Chipettes, a singing group which gives the titular chipmunk gang serious competition, a news daily reported.

"We`re strictly PG all the way. When I improvise, foul things often come out of my mouth that aren`t on the page. So I really stuck to the script or there would have been some inappropriate words from my chipmunk. It was good to do something that was very wholesome," Christina said.

"I don`t have any children, but I`m happy that I didn`t have to say anything disgusting in `The Squeakquel` that would shock kids," she added.

Christina, 38, also said mastering the high-pitched voice of her character took a surprising approach to get the right sound.

"You have to talk really slow like you just kind of had woken up from a nap. It`s really funny because it`s as far away as you can get from that chipmunk sound. Then, you hear it sped up and it`s perfect," she added.