ET is first on the set of Robert Downey Jr.'s action-packed re-imagining of 'Sherlock Holmes,' and we've got a sneak peek!

"It's pretty badass," Robert tells our own Thea Andrews, joking, "1891 Victorian England was a petty gnarly place -- I like that I actually got the word gnarly in a Victorian description."

Robert's version of Holmes is a whole lot more tough and sexy than you've ever seen before, but Robert says his take on the character was already there in print.

"I think as much as anything, the reinvention is actually a return to the idiosyncrasies that [Arthur] Conan Doyle had in his books that people hadn't really paid much attention to," he says.

'Lock, Stock and Two Smoking Barrels' director Guy Ritchie brings his unique visceral style to the movie from blockbuster producer Joel Silver, but Robert points out, "The action in the film is visceral, but not so visceral that we can't have the rating we want. This is a film that is actually really accessible to a hugely wide audience, whereas [Guy's] films, famous and influential as they were, were a little more adult. This is a very family friendly version of Sherlock Holmes."

Ritchie actually reveals that he initially wasn't sure Robert was right for the part, saying, "I didn't realize that Robert was an athlete, and gradually it transpired that he's like super fit and he's like a real martial artist."

Rachel McAdams plays Robert's love interest in the film, and says, "I was just really excited and kind of nervous [to work with Robert]. He's so incredibly talented, my nerves quickly subsided and my fears went away."

Jude Law also stars opposite Robert as Homles' trusty sidekick, Dr. Watson, and tells ET, "When I was approached I was very interested initially because Robert was playing Sherlock. It seemed to me that all his past work has been exciting and brilliant. I met him and he was a lovely man, and we seemed to be on the same page as to what can be done with the piece, what can be explored, and Guy brought to me a really fresh and intelligent take on it."

Robert's wife Susan is a producer on the film, and she observes, "Robert certainly has something in common with Sherlock -- he has this incredible brain," adding about Robert's incredible physique in the film, "he worked very hard to get [there]."

"You just get skinny, you don't eat as much and you keep working out," Robert sarcastically says about his ripped bod in the film. "I've heard people have been doing it for years."

Based on a comic book written by the film's producer Lionel Wigram, 'Sherlock Holmes' hits theaters everywhere Christmas Day.