Seann William Scott and Justin Long will also be heard in the animated 'Planet 51'

When you get an oddball cast that includes Dwayne "The Rock" Johnson, Jessica Biel, Justin Long and Seann William Scott together, chances are they're voicing characters in an animated film.

Indeed, according to the industry trade papers, those four thespians will lend their pipes to the lead characters in "Planet 51," a big budget offering that will mark New Line's first foray into the 3-D CG-animated universe.

Johnson will voice the lead character, an astronaut named Chuck Baker. When Baker lands on the mysterious Planet 51, he thinks he's alone until he discovers a race of green people living a life not-so-different from our own.

Joe Stillman, one of the writers on the first two "Shrek" films, wrote the script, with Jorge Blanco directing.

New Line has already settled on a July 24, 2009 release date.

Biel was last seen in "I Now Pronounce You Chuck & Larry" and "Next." She has "Powder Blue" and "Easy Virtue" among her upcoming films.

Johnson, who had a recent hit with "Game Plan," co-starred with "American Pie" veteran Scott in "Southland Tales."

Long was last seen in "Strange Wilderness" and heard as one of the title rodents in the smash hit "Alvin and the Chipmunks."