For the voice of Groot, Marvel approached Vin Diesel of The Fast and the Furious franchise, since both Gunn and Feige were fans of his basso profundo work as the title character in the animated film The Iron Giant. Diesel was hesitant about playing a character whose dialogue largely consisted of three words (I, am, and Groot), but when he showed his children a picture of the Guardians of the Galaxy and asked them which part they thought Marvel wanted him to play, they pointed at Groot. Diesel signed up to voice the tree.
