Lucy Liu at the Hilton San Diego Bayfront Hotel on July 12, 2012 in San Diego, California. (Christopher Polk/AFP)

Lucy Liu has praised TV bosses for thinking "outside of the box" by casting her as Sherlock Holmes’ first female Dr. Watson in new reboot ‘Elementary’.

Fans were stunned when it was announced the actress had been cast in the traditionally male role, but she insists the dynamic with co-star Jonny Lee Miller, who plays the famous detective, adds "a little bit of a tingle".

Chatting about her controversial casting at California's Comic-Con on Thursday, she told fans, "You have to be a pioneer and being a pioneer means doing things that are different and outside of the box... (Creator Rob Doherty) was really thinking outside the box... When you do stuff, it's not always to please other people. It's to please yourself."

Doherty also assured the crowd that a romance between Watson and Holmes is off the cards as he wants the show to remain true to author Sir Arthur Conan Doyle's original stories.

He said, "It's a challenge of the series to not turn it into a will-they-or-won't-they (get together). It's not about that, it's about honouring the source material and the bond.

"When this opportunity arose, I did a lot of research - psychological assessments of the original characters by actual doctors - and Holmes struggled a bit with women... There are moments when he doesn't quite get the fairer sex.

"It made me laugh - the idea of 'What would be more trying than Sherlock Holmes living with a Watson who's also a woman?'"