Musician and producer Pharrell Williams was reduced to tears as he and Oprah Winfrey talked about the "overwhelming" fan reaction to his hit single "Happy."

During an interview with Winfrey, Williams said when it was first released, the single received little airplay. It wasn't until the video was out that its popularity began to take off, he said.

"The next thing you know, we put out the video on November 21, all of a sudden boom," he said.

Inspired by Williams' video, in which he and others are seen dancing on the streets of Los Angeles, countless fans have created their own homemade versions.

From Iceland, to the Philippines, to Senegal, videos of fans ecstatically dancing in the streets now flood the Internet.

"It was no longer my song," Williams said.

At this point in the interview, Winfrey played a short montage of clips from the fan-made videos. That’s when Williams began to cry silent tears, prompting Winfrey to hand him tissues.

"Why am I crying on Oprah?" he joked, as he wiped his tears. "It's overwhelming because I love what I do, and I just appreciate the fact that people have believed in me for so long that I could make it to this point, to feel that."

Winfrey admitted that the videos made her cry as well.

"I was just thinking about your grandmother, I bet she didn't even imagine that," she said. "It's being used for something that's greater than yourself, I get that."

She later tweeted that the interview was one of her all-time favourites.

Williams responded, tweeting "You can't imagine what this means coming from you, a rare force. So radiant."

It's turning out to be a banner year for the 41-year-old hitmaker. Earlier this year, he picked up four Grammy Awards, and was nominated for an Academy Award for "Happy."

He also partnered with the UN to celebrate the International Day of Happiness on March 20. His latest album, "Girl," was released in early March.