Vin Diesel has a secret script for the Guardians Of The Galaxy movies, director James Gunn has revealed.

The 49-year-old actor plays the walking and talking tree Groot in the Marvel films opposite Chris Pratt and Zoe Saldana, and is famous for only speaking five words including: “I am Groot.”

Diesel even poked fun at his character’s less than elaborate vocabulary by wearing a T-shirt to the movie’s premiere in London back in 2014 with the words “I Am Groot” emblazoned on the front.

Now Gunn, the man behind 2014’s Guardians of the Galaxy and its sequel slated for release next year (17), has revealed he and the Fast & Furious star share a secret script.

He posted a snap of the ‘Groot Version’ of the Guardians of the Galaxy Vol. 2 screenplay on Instagram on Friday (02Sep16), and confessed only he and Diesel know the true meaning behind the inflection variations of “I am Groot.”

“The special Groot version of #GotGVol2 that only Vin Diesel & I have, where every Groot line is printed in English,” Gunn said in his post.

Up until now, it was thought nobody knew what Groot meant apart from his raccoon pal Rocket, voiced by Bradley Cooper.

Guardians of the Galaxy Vol. 2, also starring Kurt Russell, Dave Bautista and Karen Gillan, will open on 5 May, 2017.