Since this is seems to be Guardians Of The Galaxy day, here's the story of how Vin Diesel got the voice of Groot in the upcoming film. Which will consist of him saying "I am Groot" and nothing else for the duration of the movie.
This is how it was told to me by a senior Marvel Comics executive, at any road.
A while ago, Vin Diesel posted the following on Facebook last summer, just before San Diego Comic Con.
"Marvel has requested a meeting … no idea what for … haha, you probably know better than me."
There was much commotion, the post was taken down and people wondered what was going on. He then posted about a follow up meeting.
The truth? Vin Diesel had made it up. That's according to this Marvel Comics exec. They told me that Marvel had not requested an initial meeting, Vin Diesel was just playing around with social media and may not have realised the geekstorm that his words may have caused. And the voice of Groot had not been cast.
However Marvel noticed the geekstorm. Had a few words. And had a meeting. Found him Groot. And the rest is history.
Basically, Vin Diesel pulled a Mark Millar. And it worked just as well!