Christina Applegate is now family to Drew Barrymore.

A source exclusively reveals to me that the Samantha Who? star has signed on for a role in Going the Distance, a romantic comedy starring Barrymore and her maybe-real-life boyfriend Justin Long as a couple in a long-distance relationship…

Applegate will play big sister to Barrymore’s character, according to my source.

It’s Always Sunny in Philadelphia star Charlie Day has also joined the cast, playing a friend of Long’s, the source said.

Directed by Nanette Burstein, the New Line flick begins shooting July 15 in New York City. Adam Shankman and Jennifer Gibgot are producing.

Reps for Applegate and Day confirmed their new gigs.

Applegate was last seen on the big screen opposite Rainn Wilson in The Rocker. We’ll see—well, hear—her come Christmastime in Alvin and the Chipmunks: The Squeakquel, a follow-up to 2007’s Alvin.

Samantha Who? was recently canceled by ABC, but remaining episodes are airing throughout the summer.

Source: eonline.com