Vin Diesel says audiences haven't seen a "fully-fledged" Groot yet.
Vin Diesel
The 49-year-old actor voices the fictional tree-like alien superhero in the 'Guardians of the Galaxy' series, and has said the versions of the character seen in the two instalments so far have not yet been Groot at his full potential.
Speaking to USA Today, the star said: "The first Groot we saw was a freshman in college. This ['Guardians of the Galaxy Vol. 2'] Groot is in nursery school. Wait 'til we see the full-fledged working-man Groot. Wait 'til we see GROOT!"
Meanwhile, Vin previously stated it was "challenge" to voice the character despite the alien's vocabulary only stretching to the three-word phrase "I am Groot", as he had to convey so much emotion just through that one phrase.
He said: "It's very, very challenging because you're limited to three words. There's a secret script that I get where it has all of Groot's lines, but the catch of it all is the only was I can say it is: 'I am Groot.'"
And he admitted in a separate interview that the "secret script" he is given makes the character so much more "fun" to voice, as he gets to understand the character more.
He revealed: "Groot is always challenging to play. As an audience what you hear is, 'I am Groot', but he is expressing himself and you have to try and convey what he intends to say and his emotions in those three words.
"I actually had a secret script where I was told what Groot was trying to say. That made him a lot of fun to voice."
Though Groot sacrificed himself at the end of the 2014 movie, Vin is back again in 'Guardians of the Galaxy Vol. 2' voicing Baby Groot, and thinks the two characters are very different.
He said: "Groot in the first movie was a college-level Groot. He might have had some growing up to do, but essentially he had the mind of a man.
"After he sacrificed himself he has to start again. Baby Groot is naïve. He has to learn everything again."
But the actor is hoping to return as Groot in 'Avengers: Infinity Wars' next year.
He said: "I've never hidden my excitement at Groot and The Hulk going toe-to-toe in The Marvel Universe.
"Obviously not Baby Groot. I talked to The Russo Brothers about that - so that might be something for fans to look out for!"
Tagged in Vin Diesel