"I actually did, [to] Cee Lo," Williams said. "He sounded amazing on it. I mean, he burns my version!
"But the ... how do I say this diplomatically? Um ... he ... um ... The powers that be, at the time, did not see it fit for him. Some folks on his team just felt that the priority should be on [Cee Lo's] album at the time, so they elected not to do that song," he added.
Williams assured Stern that Green wasn't too upset about the "Happy's" eventual success.
"It's not his fault -- he was totally down with it … [and] he was one of the most gracious people about it when [the song] came out."
2014: The Year in Music [PHOTOS]