Vin Diesel seemingly took a great deal of inspiration from Groot’s gentleness. While the alien tree person did occasionally help out on a battlefield, he seemed blissfully relaxed most of the time, taking in the world the way a child might. In the “Guardians of the Galaxy” sequel, Baby Groot was literally a child. For an actor like Diesel, whose stock in trade had become playing tough and grizzled characters, Baby Groot was a change of pace. Additionally, the role allowed him to be gentler and more emotional than he had ever been before. The gentleness let the actor appreciate life — and the life of a friend — more openly. He said: 

“When we deal with death, our appreciation for life is represented in so many ways. […] We appreciate everything that’s alive … And this character celebrates life, in so many ways. It’s the most innocent character I’ve ever played, clearly, which is why I’ve kind of been so silly. I’m not talking about heavy issues that I’m usually talking about with the movies I make … I get to have fun!”

As one can imagine, playing just the voice of Groot — a character who can only say three words — was a challenge Diesel had never encountered before. He was facing the same challenges as Ikue Otani, the actor who plays Pikachu (who can only say one word). With such a limited instrument, Diesel had to find new ways to express emotion. He said: 

“I was being challenged as an actor, as a thespian … the idea of playing a character without any facial mannerisms or allowing your body physicality to play into the character, and being limited to such a small vocabulary.”