AceShowbiz -

Not having trouble with his portrayal of Tony Stark in "Iron Man" and its sequel, Robert Downey Jr. confessed that starring as one particular legendary detective for Guy Ritchie's "Sherlock Holmes" is hard. "Sherlock Holmes is easily the toughest job I've ever had," the actor stated in an interview with MTV.

During the interview, Downey also shared his thought on his titular character by describing him as "a total badass." He then elaborated his remark, saying "He thinks through all eventualities, possibilities and counterattacks when he's fighting, so he actually has the fight worked out before he starts."

Downey further compared Holmes with his character in "Iron Man". Detailing the differences between Stark and Holmes, he said Stark "is cool, and sometimes if I get pumped-up enough and take enough creatine, then I can look cool for up to 12 seconds at a time." He continued, "With Sherlock, it was very different. He's a much more centered and focused person, which works for me. I'm a character actor."

"Sherlock Holmes" is based on Lionel Wigram's upcoming comic book. The movie will send Holmes and his partner Watson on their latest challenge. Revealing fighting skills as lethal as his legendary intellect, Holmes will battle as never before to bring down a new nemesis and unravel a deadly plot that could destroy the country.

Joining Robert Downey Jr. in the cast ensemble are Jude Law, who plays Watson, and Rachel McAdams, who stars as Holmes' love interest Irene Adler. Meanwhile, Holmes' arch nemesis Lord Blackwood is portrayed by Mark Strong. The movie itself will be released in U.S. theaters on December 25.

Robert Downey Jr. recently has completed the production of "Iron Man 2". He is also attached to reprise his role as Iron Man in "The Avengers", another Marvel adaption film which brings together superhero characters from the comic books.