One 'Doctor Who' fan got the surprise of her lifetime at Fan Expo in Toronto on Friday, as actor Matt Smith helped the woman's boyfriend propose to her in front of a packed crowd.

Smith, who recently finished playing Doctor Who in the British series, was holding a one-hour fan Q&A at Fan Expo on Friday morning.

And, with the opportunity to ask the last audience question, Doctor Who fan Brandon Leonard dropped "The Question."

"Uh oh..." Smith said on stage, after Leonard produced a Doctor Who TARDIS ring box and asked for his help with the proposal.

The TARDIS looks like a blue British police box, and can travel through time.

Smith gamely agreed to help, and called up Leonard's girlfriend, Annalyssa.

"Annalyssa, will you marry me?" Leonard said into the microphone.

The audience rose to its feet, and Annalyssa said something too quiet for the microphone to hear.

"She said yes!" Smith crowed. "Thank God she said yes!"

He then signed the TARDIS ring box for the happy couple. "Have the most happy marriage," Smith told them. "I hope you're a good cook," he added to Annalyssa.

Life after the Doctor

The 31-year-old British actor was relaxed and engaging in his first Toronto appearance since he finished playing the Eleventh Doctor on the sci-fi series. Dressed in dark jeans and a faded denim jacket, Smith fielded many Doctor Who questions, and nearly as many fan requests.

Smith sprinted across the stage with one fan, as the two pretended to flee a horrible danger behind them. He also snapped an on-stage selfie with a gleeful teen, and answered an "I love you!" catcall with "Lady from Canada whose name I don't know, I love you too!"

Smith admitted that he’s both relieved and saddened to watch as the long-running 'Doctor Who' series moves on without him. The show, whose main character "regenerates" with a new face every few years, recently replaced Smith with actor Peter Capaldi.

But Smith's departure after six seasons was his own choice. "I sort of felt like I had to," he said. "It was time."

'Doctor Who' marked its 50th anniversary late last year with a special episode gathering many past Doctors for one show.

Smith said the show owes its longevity to the versatility of its premise.

Essentially, 'Doctor Who' can go to any point in time or space to tell a story.

He said he'd never seen a full 'Doctor Who' episode when he took on the role, but now, he's become a fan.

"It's a cultural institution," he told fans at Fan Expo. "It's not just a job."

The audience was dotted with some wearing the signature Doctor Who outfit and bowtie, with others wearing the fez hat that Smith's Doctor often wore in the show.

Guess Who's engaged?

After Smith's talk, Brandon Leonard and fiancée Annalyssa were all smiles.

"Is this even real life?" Annalyssa said. "What's happening?"

Leonard said he'd been planning the proposal for a while, but it nearly didn't happen because he wasn't at the front of the line for the last question.

"I ran to the front of the line and pleaded my case to the guy in front, and he let me go," Leonard said.

"I'm just so shocked, and very happy of course," Annalyssa said.