SAN DIEGO — The 12th Doctor bid a fond farewell to Comic-Con Sunday.

The Doctor Who faithful gave Peter Capaldi a standing ovation and a rousing sendoff before he leaves the long-running British sci-fi show following the upcoming Christmas special.

"Time ran away form me. I don’t know how we got here so quickly," said Capaldi, who's been playing the Doctor since 2013. He also paid tribute to the fans and meeting them over the years: "To realize the show is so popular and beloved all over the world, it’s remarkable to find yourself in the center of that.”

Titled "Twice Upon a Time," the Christmas special teams the 12th Doctor with the First Doctor (David Bradley, re-creating William Hartnell's Doctor from the 1960s) on a World War I adventure where both men refuse to regenerate and "decide whether or not they’ll carry on, which they will," said executive producer and writer Steven Moffat.

The episode also marks the Who finale for Moffat — Chris Chibnall takes over next year — and Pearl Mackie as the Doctor's companion, Bill Potts.

Mackie also said goodbye to fans. "I don’t think I was prepared for how powerful the Doctor Who fandom is."

Capaldi joked that his Doctor will always be his favorite. "I love him. He’s certainly the most handsome, in my eyes. His hair had the biggest arc."

But he always made sure to play him as an alien.

"I don’t know what kind of creature he is. We perceive him as a human, but I don’t think that's he is. He’s stranger and darker and cleverer."

Jodie Whittaker was announced as the 13th — and first female — Doctor last week, and Capaldi applauded the pick.

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"I think Jodie’s going to be amazing," he said. "She’s so full of excitement and so full of passion about the show. It’s thrilling that it’s in the hands of someone who cares about it so deeply. She’s a great choice."