Published Monday, 14 April 2014
During the interview he confessed he had been at his lowest point creatively when he penned his Oscar-nominated song.
The producer and hitmaker admitted he had been all "out of ideas" when he sat down to write the Despicable Me 2 theme song, claiming his effort was a "crazy, half-court shot" and revealing he is still so blown away by its monumental success.
He explained: "It's not because you're that good (that you can write a song like Happy). It's because you're out of ideas. And that's what happened. I hit zero. And I just hit a place of openness because I had nothing else left."
Winfrey then shared a video of fans from around the world dancing to Happy, prompting Williams to shed tears of joy and quip: "Why am I crying on Oprah?"
Turning serious, he added: "It's overwhelming because I love what I do and I just appreciate the fact that like, people have believed in me (for) so long, that I could make it to this point to feel that (the joy of the fan video)."
During the Oprah Prime interview, which aired in the US on Sunday, Williams also revealed that he usually comes up with his best ideas in the shower or while in the air.
He said: "Either when I have a really good gut feeling about something, it's written in the shower or on a plane. The water (in a shower) attracts your ear. You get distracted, and your mind wanders."