It's a query that's always surrounded the heroic Doctor of the British sci-fi franchise Doctor Who, which celebrates its 50th anniversary next year, and part of a continuing story line that goes into the show's seventh series later this year on BBC America.
"It's been there from the start. Other Time Lords have had names — he never gives his," executive producer Steven Moffat said at a packed Comic-Con panel for the show. "Obviously the question is tremendously important and only I know why.
"We'll find out the truth."
Even the guy who plays the current Doctor, Matt Smith, is still in the dark. "He knows and he won't tell me!" the British actor said, with Moffat responding: "You'll see."
This weekend marked the second time in a row Doctor Who has headlined Hall H, the main Comic-Con exhibition hall at the San Diego Convention Center, and the stars felt the adoration from fans.
"If the world was a bit more like Comic-Con, it would be a better place," Smith said.
Karen Gillan, who plays the Doctor's companion Amy Pond, said she came down an elevator with a girl dressed up as a villainous robot Dalek. "It took a little bit for us to register each other."
"You can be in the lift and just be like, 'Hey Batman, how's it going?' " said Arthur Darvill, who stars as Amy's husband, Rory Williams.
The upcoming series will feature the Doctor, Amy and Rory time-traveling in the TARDIS back to America's past for an old-timey Western episode — filmed in Spain — as well as more Daleks than have ever been seen in one place before, an amorous Queen Nefertiti, the return of the creepy Weeping Angels, and dinosaurs on a spaceship.
"I don't think we've ever had a bigger variety of episodes than the ones we'll show you," Moffat said.
This year will also mark the departure of Gillan and Darvill from the show, with Jenna-Louise Coleman joining Doctor Who as the new companion.
"It's a climactic and fitting ending to my two favorite companions," Smith said.
"I didn't stop crying for two weeks. Anything would set me off. Tender stem broccoli, anything!" said Gillan, who will be starring in the new British series Broadchurch with the previous Doctor, David Tennant.
"I'm going to miss running down corridors away from monsters-aasome of them are rather rude. I can look really scared at tennis balls now," the actress added, referring to the stand-ins for the computer-generated creatures often seen on Doctor Who.
Actors coming and going from the program is just one aspect that makes Doctor Who special and adds to its variety, according to Smith.
"The show is the star and the show will continue without us. That's the thing we're here to serve," he said. "It is about regeneration and welcoming in Jenna and a new time. That's what's exciting.
"Each week it can be anything and you're not bound by genre. You can tell a horror story one week, and a rom-commy one the next."