Robert Downey Jr. set his crotch on fire while shooting his new film. The actor, who plays fictional British detective Sherlock Holmes in Guy Ritchie\'s latest project, was smoking the character\'s famous pipe in one scene when the ash fell onto his lap and set his trousers alight. A source said: "Robert leaped from his armchair and jumped up and down, slapping his crotch and howling, \'Oh God, I\'m on fire!\' Robert had placed the pipe on a plate on the arm of the chair, but it overbalanced and plopped into his lap, scattering lit tobacco all over his pants." Luckily, Robert\'s co-star Jude Law - who plays Holmes\' sidekick Dr. Watson in the movie - was on hand to extinguish the flames and save the star from singeing his privates. The source added: "While Robert was screaming and swatting his pants, quick-thinking Jude saved the day by flinging water from a flower vase at Robert\'s naughty area." Robert emerged unscathed from the incident, but production was halted while the wardrobe department found him a new pair of trousers to wear.