Musician and producer Pharrell Williams is usually known for a larger-than-life personality and almost bottomless supply of self-confidence.

But his bravado momentarily cracked on an interview with Oprah Winfrey when he watched a montage of tribute videos to his 2013 hit Happy.

In a sit-down interview with Oprah Winfrey on her channel OWN, Williams begins with his usual bravado, marvelling at the exploding popularity of Happy once the music video hit YouTube.

"We put out the video on Nov. 21, all of a sudden... boom," said Pharrell, sporting a forest green version of his trademark, sort-of-RCMP-style hat.

Discussion then turned to the dozens or more tribute versions of the song fans have since uploaded to YouTube themselves.

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

Winfrey then played a montage of the fans' videos. Every clip featured fans dancing along, from locations like Detroit, London and Washington, D.C., to Slovakia, Thailand and Malawi.

Williams then breathes deeply, and breaks down in tears. Winfrey hands him tissues as he struggles to find words.

"Why am I crying on Oprah?" he chokes.

"You know, I was just thinking of your grandmother, I bet she didn't even imagine that,' said Winfrey, which probably didn't help stem the waterworks.

He continued, "It's overwhelming, because I love what I do, and ...(pauses) 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."

Happy, which was featured in the animated film Despicable Me 2, was nominated at this year's Academy Awards for Best Original Song. It lost to Kristen Anderson-Lopez's Let it Go, from Frozen.

The official music video for Happy currently boasts more than 182 million views. The Despicable Me 2 version, featuring the film's yellow, googly-eyed Minions dancing to the lyrics, has more than 26 million views.