It was finally announced earlier this month that Vin Diesel is portraying Groot in Guardians of the Galaxy, after weeks of speculation when the actor revealed in June he had a meeting with Marvel. While doing press for his upcoming sci-fi thriller Riddick, the actor confirmed that he will bring Groot to life with the use of motion capture technology.
"It'll be voiceover, MoCap and all of that stuff. It's going to be super cool."
The actor also spoke about those early meetings with Marvel, revealing he was in talks for an unspecified character that would be a part of Marvel Phase Three.
"What we were initially talking about was a fresh IP (intellectual property), and that was the focus of our conversation. A fresh IP that would come out in 2016 or 2017 to potentially launch a third phase. When we went to Comic-Con, we realized that we wanted something more immediate. With my schedule, it was almost impossible to imagine I could do anything immediate. I guess after they watched The Iron Giant, or whatever, they came up with this idea of taking the strangest Marvel character -- or the strangest Marvel character that's ever hit film -- and thought what I could do with that with motion capture and with my voice."
Vin Diesel revealed that his deal for Groot has not been finalized, so it is possible he still could play this mystery character as well in Marvel Phase Three. As of now, only Ant-Man, which is set for release on November 1, 2015, has been confirmed for Marvel Phase Three.