LOS ANGELES — “Doctor Who” star Jenna-Louise Coleman has been warned. She knows that two months from now, fans at Comic-Con International in San Diego will line up in the thousands, camping overnight outside the city’s convention center to secure seats for the annual panel devoted to the BBC TV sensation. Many will wield sonic screwdrivers or wear Dalek costumes, and more than a few will come dressed as Coleman’s character, Clara.

But back in March, the hype hadn’t caught up with her.

“Everyone wants to know, ‘Has your life changed since joining the show?’” Coleman said over a lunch of baby beets and tangerine at downtown Los Angeles’ Lazy Ox Canteen. “And I’m like, ‘No, not really.’ I just go to Cardiff, and I do mad things and experience mad stuff on set, and then I come back to my London life, which suddenly seems more boring because I’ve been blasting Cybermen.”

Though “Doctor Who” is something of a British institution, celebrating its 50th anniversary this year, stateside the series about the eccentric time-traveling alien has long been relegated to the realm of cultish fandom. But with its 2005 revival and reboot, the show has enjoyed a crossover into the American mainstream, drawing more than 2 million viewers for its BBC America midseason premiere this March.

The current season wraps up May 18, marking the third space tour for Matt Smith as the Doctor, the 11th actor to play the character in the series over the decades, and the first for Coleman’s Clara Oswald, the latest in a long line of so-called companions, partners who travel with the Doctor to assist him in his Earth-saving and otherworldly sleuthing.

Like many companions throughout the show’s history, Clara serves as an audience surrogate, helping make the show’s outlandish story lines — which can involve alien races, other planets and futuristic technology — become more relatable.

“It’s normally me being like, ‘What? Why? How?’” Coleman said, chuckling. “I’m more of the audience asking, and Matt has the dialogue and the jargon. I’m very much the human.”

Coleman, 27, has been performing since she was a teenager attending school in Lancashire, in northwest England. She loved trips to the theater and acted in the Edinburgh Festival Fringe when she was 18. She landed her first job playing Jasmine Thomas, the niece of the local vicar, in the long-running British soap opera “Emmerdale” while auditioning for drama schools.

“People always refer back to that role,” she said. “It’s the vicar’s niece, so that’s all I used to get from people walking down the street, like ‘Does the vicar know you’re out this late?’ That kind of thing.”

She ultimately chose to forgo formal training, opting instead to continue working in television and taking occasional night classes.

“I thought, if I go to drama school for three years, I’m going to be like 28 when I come out, and then there’s all that playing age I’m going to miss in the middle,” she said. “You try to learn on the job.”

She landed roles in the BBC drama “Waterloo Road” and in Julian Fellowes’ “Titanic” miniseries, in addition to some smaller indie films and a bit part in “Captain America: The First Avenger.” But her turn on “Doctor Who” might prove to be what raises her professional profile in the U.S.

When she auditioned, she recalled that Smith greeted her with a hug, and instead of watching her from behind a desk, they worked on several scenes together.

“I had prepared my scenes in a certain way, like you do, and Matt knocked all of that out the window and totally surprised me, and in surprising me, it felt very spontaneous between the two of us, and that was really exciting,” she said.

At 5 feet 2, Coleman stands a full head shorter than Smith, but as Clara, the diminutive actress matches Smith’s audacious Doctor toe to toe in spirited banter. Coleman possesses a ready smile, punctuated by dimples, and expressive brown eyes that sparkle with contained mischief when she teases Smith on screen.

“She’s up for a bit of banter, and she holds her own,” Coleman said. “She’s definitely a match for the Doctor. She’s not intimidated by him. She’s curious. She finds him amazing and ridiculous in equal measures, but she mentions the ridiculous a bit more often.”

The playfully combative companionship between the Doctor and Clara was inspired partly by Indiana Jones and Marion Ravenwood in “Raiders of the Lost Ark,” which Coleman watched at Smith’s urging.

“I really loved their sparky kind of relationship,” Coleman said. “He’s like, ‘You wait here,’ and she’s like, ‘I’m not waiting here, I’m coming with you!’”

Coleman’s performance so far has been well-received by Whovians, who are quick to draw parallels between Clara, a nanny in contemporary London, and previous companions. Los Angeles Times critic Robert Lloyd described the character as “very clever, and a little bit impudent” and “young, pretty, spunky and self-possessed.”

Coleman currently is back in the U.K. She just finished shooting the feature-length “Doctor Who” 50th anniversary special, which will be released theatrically and in 3-D in Britain in November, in addition to airing on BBC One. The special, which will feature previous Doctors and companions, will be televised in the U.S. on BBC America.

She’ll return to the States this summer for Comic-Con, where some 6,500 fans are expected to gather in the venue’s largest hall for the panel devoted to the series.