Doctor Who fans can expect a "fiercer" version of the timelord according to Peter Capaldi - the latest man to take the controls of the tardis.
The actor, who met fans at the first screening of new episode Deep Breath, in Cardiff, said playing the part was "a gas".
He said: "It's very exciting being Doctor Who, you wake up in the morning and you don't know which monsters you're going to face or which new planet or alien landscape you're going to see".
Asked about his version of the science-fiction hero, he said: "He's a fun Doctor, he's a bit fiercer perhaps than some of the other ones.
"He's a little more difficult to get on with I think but he's good fun, he likes a laugh and he's also quite tough."
His co-star Jenna Coleman said the new series had "a different pace, a different feel, the Doctor is darker, more enigmatic".
Thousands of fans from across the globe descended on Cardiff to give Peter a rousing welcome ahead of his debut performance.
A navy blue-suited Peter, and Jenna, who turned heads in an elegant red dress, were greeted with cheers from die-hard fans the moment they stepped out of their chaffeur-driven Mercedes and walked up the red carpet, signing autographs and dodging a few daleks in the process.
Tickets to catch a glimpse of Peter in the Doctor's role were snapped up within minutes - with some fans travelling from as far as France, Japan and the United States.
The show's writer Steven Moffat said he was impressed by the turnout in Cardiff - which brought the usually busy shopping centre The Hayes to a complete standstill.
"I've been to some big premieres in LA, and the turnout and response here has been even better than those," he added.
Among those standing behind the crowd barriers hoping to catch an autograph with the 12th Doctor and his assistant were the Fedderson family from Chicago.
They had originally booked a holiday to France, but decided to amend their plans when they heard the premiere was happening in Cardiff two weeks ago.
Mother Kristan, 47, said: "My husband Brett and I have been fans of the show since the 1980s.
"We couldn't believe we were going to be in Europe when the premiere was happening, so we knew we had to come across to Cardiff.
"Our daughters Taylor and Lauren have become big fans of the show as well. So I woke up at 3.30am so I could call the hotline to get tickets to the premiere. Amazingly we got the last set of tickets so we're overjoyed."
During a question-and-answer session with fans Peter was asked what his infamous character Malcolm Tucker, from political comedy The Thick of It All, would have made of the Doctor.
He replied: "He would probably be jealous. I think he would be incredibly envious that me, his alter ego, had got such a big gig."
Sci-fi fan Peter also credited Doctor Who with teaching him how to act - saying that he felt he had been "brought up" by the first four actors to play the role - William Hartnell, Patrick Troughton, Jon Pertwee and Tom Baker.
"It's every young boy's dream to be Doctor Who," he said. "If I could go back in time and speak to you, my younger self, I'd tell him keep drawing those comics of yours and keep writing to the BBC."
Peter - like Steven and Jenna - said he could not give too much away about the new series.
However, the Glaswegian said fans could expect a change in the relationship between the Doctor and Clara. He said the pair still loved one another deeply, but that love went beyond romance.
He also gave details of his "unusual" audition for the show - which the show's producers wanted to keep so secret they staged it at his house.
"I didn't know this at the time but I was first on their list and the only person they intended auditioning," he added.
:: The new series of Doctor Who begins on BBC1 on Saturday, August 23.