Game Of Thrones Season 4 Filming Already Completed For Mark Gatiss: Sherlock Actor Admits 'My Life Is Entirely Composed Of Fan Obsession'

As "Game of Thrones" hits the San Diego Comic-Con, Mark Gatiss is pulling double duty due to his recent casting news on the HBO series, and his acting/producing gig with "Sherlock."

During a recent chat at Comic-Con with CNN, Gatiss reveals he is already done filming for "Game of Thrones," which may be a relief for "Sherlock" fans since production is still underway for the BBC darling.

"What's interesting is that it's such a huge, sprawling cast and people seem to be there for ages, but they actually shoot two or three days and that's it," says the actor, who portrays Mycroft on "Sherlock."

"Once it's put together it looks like everybody must be there for weeks and weeks and weeks."

But despite filming being completed for "Game of Thrones" season 4, Gatiss is unwilling to divulge any information on his character.

"I'm not allowed to tell you," admits the "Doctor Who" writer.

"I've done my filming. I'm glad I didn't tell anyone before this since it's a big secret. The announcement of [my casting] was obviously timed for Comic-Con and I'm rather overwhelmed with the reaction, honestly. It's a great show with so many brilliant people in it."

Between "Sherlock," "Game of Thrones," and "Doctor Who," Gatiss seems perfectly prepared for the fandom that will hit once season 4 rolls around.

"My life is entirely composed of fan obsession, so this is just another one to add to it. It's all a Venn diagram."