Marvel confirmed the news earlier today via its website:
Academy Award-nominated actor Bradley Cooper has officially joined the cast of Marvel's "Guardians of the Galaxy," lending his voice to the fan-favorite raccoon that will join Peter Quill (Chris Pratt), Gamora (Zoe Saldana) and Drax (Dave Bautista) on their epic adventure.
Marvel's announcement also points out that Cooper's role in "Guardians" will be the actor's first dive into the world of voiceover work, something that may be hard to believe given the length of the actor's career. Nevertheless, it's true.
Marvel's announcement comes on the heels of the all-but-confirmed-at-this-point report that Vin Diesel, who is no stranger to voiceover work (just watch the amazing Brad Bird-directed "Iron Giant"), will be voicing Rocket Raccoon's brutish partner-in-crime, Groot.
Given this news, how amazing the footage was at Comic-Con, and that the cast already includes Chris Pratt, Zoe Saldana, Glenn Close, John C. Reilly, Benicio Del Toro, Lee Pace, and Michael Rooker (to name a few), we'll be first in line when "Guardians of the Galaxy" hits theaters August 1, 2014.