Valerie Kalfrin

Bradley Cooper, Vin Diesel and Voice Acting

Rocket Groot“Guardians of the Galaxy” is one of the freshest sci-fi hits in years thanks to its loopy humor, stunning visuals, characters’ chemistry, and amazing voice actors. Earning a record $94 million for an August debut, the Marvel Studios film has charmed critics and audiences alike with its motley ensemble of heroes led by Chris Pratt as a “blissfully spaced-out space crusader” who calls himself Star-Lord. He’s joined by a sly assassin (Zoe Saldana), a muscular madman (Dave Bautista), and two computer-generated tough guys who happen to be: a genetically altered raccoon named Rocket and a sentient tree that speaks but one phrase: “I am Groot.”

Voiced respectively by Bradley Cooper and Vin Diesel, Rocket and Groot steal moviegoers’ hearts both through delicate animation and deeply layered performances. Cooper channels his angry but troubled “Silver Linings Playbook” character more than his “Hangover” swagger for Rocket: “Cooper is so good at finding the pathos in his existentially conflicted critter that you half expect the little guy to plead ‘I am not an animal!’ Except, of course, he is,” Variety wrote. Diesel, whose gravelly tones brought soul to the hulking robot in 1999’s “The Iron Giant,” taps similar reserves of loyalty, strength, and childlike innocence for Groot. “He ends up conveying so much heart, so much fascinating emotion, that it’s hard to believe he only speaks four words in the film,” HitFix said.

On Word and Film today, I look at a selection of roles where an actor rose to the challenge of acting solely with his or her voice in films such as “2001: A Space Odyssey” and “Her.”