When Macklemore and Ryan Lewis released their song "Same Love" in 2012, it became a sort of unofficial anthem for same-sex marriage. The lyrics advocating for LGBT rights were both powerful and beautiful, and the chorus -- performed by Seattle artist Mary Lambert -- was equally intoxicating.

"Same Love" quickly climbed the Billboard charts and for a relatively unknown artist like Lambert, instant fame was a whirlwind. Especially considering that she calls herself the "last resort" option to sing on that track.

As Lambert tells "Oprah: Where Are They Now -- Extra," Macklemore and Ryan Lewis had finished the song and were looking for someone to come up with the chorus when her name came up.

"They had asked pretty much every gay artist you can think of to sing on this song and everybody turned it down," Lambert says. "I was the last resort. I mean, I was playing venues to, like, 10 people!"

But a phone call from a friend was about to change that.