Rebecca's Emotional 'This Is Us' Song Was Written By Mandy Moore's Fiancé & It's The Sweetest Collab Ever — VIDEO

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If you've only just finished crying over the most recent episode of This Is Us, you might want to get yourself a fresh box of tissues. It turns out that the moving, folk-inspired song that Rebecca sang for Jack (Milo Ventimiglia) holds even more sentimental significance than fans could have possibly imagined. Rebecca's emotional This Is Us song was actually written by Mandy Moore's fiancé Taylor Goldsmith specifically for the show. The emotional song, "Invisible Ink," was performed by Moore's character, Rebecca, in the episode "Sometimes," which aired on Tuesday, Nov. 13.

According to Entertainment Weekly, though Moore and Goldsmith often work together off-set, it was actually This Is Us' composer, Siddhartha Khosla, who thought to approach the Dawes frontman and see if he would be willing to collaborate on a song. "Dan [Fogelman, the show's creator] had sent me an email and said, 'There's going to be an original song coming up for Mandy to sing. It's going to take place in the '70s, and it's going to be Joni Mitchell inspired,'" Khosla said in a behind-the-scenes clip. "I remember going home and being like, 'I'm dying to work with Taylor on something.' I'm a huge fan of his work."

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Moore was completely shocked by Khosla's offer, but revealed that having Goldsmith work on something for This Is Us made the moment so much more meaningful for her. “Sid approached Taylor outside of me — they did it on their own. It was such a surprise," she told EW. "That my own soon-to-be-husband got to write from my character’s perspective was pretty meta and weird, but it was so cool. The song is really beautiful."

As for Goldsmith, the singer-songwriter said that joining the world of This Is Us was both exciting and incredibly easy. "I was thrilled to get that call," Goldsmith said, adding, "Sid had a whole plan of attack, how to emotionally kind of guide us with what’s going with Rebecca, and he gave me all the tools to help contribute what I could." He went on in the behind-the-scenes clip. "To hear [Mandy] in that room, it was immediately like, 'Oh my gosh, This Is Us!'" the Dawes frontman revealed. "It immediately sounded like the show."

This Is Us on YouTube

Of course, "Invisible Ink" is far from the first time that Moore and Goldsmith have worked on music together. During an appearance on Jimmy Kimmel Live! back in July, Moore explained that "music is a constant thread in our house." While teasing that she was "dipping her toe" back into recording music after a ten year hiatus, Moore also revealed that there is a possibility that her highly-anticipated comeback album may include a duet between her and her multi-talented fiancé. "Maybe we will!" she teased. "But we write together, and we sing together, and I sing on his records, and I want him to come play on my record."

With all of the love and passion that these two share for one another and for their music, it's no surprise that having Goldsmith contribute to This Is Us resulted in one of the most poignant and devastating moments that the show has created — and considering that This Is Us is full of ugly-cry moments, that's certainly saying something. Besides, "Invisible Ink" has also offered fans a chance to see what a potential Moore-Goldsmith musical collaboration would sound like, and that's truly an idea beautiful enough to bring even the most cynical among us to tears.