Who would figure playing a humanoid plant with a limited vocabulary would be so good for the soul? That's what happened to Vin Diesel, who started performing as Groot in Marvel's Guardians of the Galaxy a short time after Walker had died in a car accident. “That was healing for me,” Diesel told Variety. “To play a character that could reincarnate, rejuvenate and represent life as trees do.”

Diesel focused his energy on getting Groot's voice just right. James Gunn, who directed Guardians of the Galaxy, said Diesel performed "at least 500" takes of each "I am Groot" line and even voiced the line in "all of the different languages." Through time and meditation Diesel was able to find the right balance for the character's voice that would be powerful but not threatening. “He needed to have this guttural voice, without always being so menacing. I just played with it and played with it, and I was inspired by my 3-year-old son at the time, who I was playing the role for," Diesel explained. "I always imagined the character would have to connect to a child.”

James Gunn credits Diesel's talent and strong work ethic for making “the character suddenly became real and most people’s favorite character.”

At the end of the first film, Groot sacrificed his life and then came back as a dancing baby version of himself, but Gunn teases that we'll see some changes when

Furious 7 races into theaters April 3, 2015.