Mandy Moore Is Bumpin' in Throwback 'This Is Us' Photo

Mandy Moore threw it all the way back to the first episode of This Is Us before the award-winning drama even had title.

In the "flashback Friday" photo, Moore rocks a triplet-sized baby bump as she takes a mirror selfie in character as Rebecca Pearson. She also dons a white T-shirt, jean capris and clogs in front of the wood paneling setting, in true 1970s fashion.

Longtime fans of the show will notice Moore's bra on the outside of her shirt, a reference to the "birthday dance" Rebecca does for Jack (Milo Ventimiglia) every year — including the year when she can't fit into her old sexy lingerie.

"Day 1 of the 'Untitled Dan Fogelman Project' that eventually became #ThisIsUs," Moore captioned the photo, revealing that the NBC hit was named after its creator Dan Fogelman before it had its official title.

Fans of the show took to the comments to gush over the pilot episode as well as the series overall.

"Please know that you've healed so many hearts by being part of this untitled project," one person wrote.

"It's such a wonderful show! So much emotion and compassion! Thank you!" another wrote.

"I loved this scene! Thought it was so cute," someone said.

"Best show!! You guys kill it in every episode. Its like each and every one of you were meant for the role. Can't wait until September," another fan wrote.

Fans are eagerly anticipating the third season of This Is Us, which is set to premiere Tuesday, Sept. 25. While not many details are known about the upcoming season, viewers expect to learn more about Jack's background before he met Rebecca — namely, his time in the Vietnam War and the loss of his brother, Nicky.

In a photo shared from set last month, Moore and Ventimiglia act onscreen as Rebecca and Jack on a date at what appears to be a carnival. "This photo might be black and white, but their love is full of color," the show's official Twitter account captioned the image.

This photo might be black and white, but their love is full of color. #ThisIsUs | 📷: @roxyolin pic.twitter.com/IYqufHn7Nm

— This Is Us (@NBCThisisUs) July 23, 2018

Beth Pearson, Randall Pearson's wife, might also play a significant role in season 3. At the end of season 2, viewers saw a flash-forward with Randall and an adult version of his daughter, Tess, preparing to visit a woman referred to as "her," leading fans to speculate that Beth is on her deathbed.

However, Susan Kelechi Watson, who plays Beth, assured fans that her character is not dying.

"My mom was like, 'I'm not going to watch this show next season,'" Watson told Entertainment Weekly. "I was like, 'Why?' She's like, 'Because they're going to kill you, and I don't like it.' And I was like, 'Mom, they're not going to kill me!' [Creator Dan Fogelman] and I spoke about it — they're not going to kill Beth. She's going to survive. It feels good to know."

And even though the series finale is likely years away, Moore said last month that she is among the select few who knows how it will end — and says viewers will be satisfied by the ending.

"I think the ending will be very satisfying for people," Moore said on Jimmy Kimmel Live! in July. "I think it's very true to what the show evokes from all of us. People will feel their feelings."

Season 3 of This Is Us premieres Tuesday, Sept. 25 at 9 p.m. ET on NBC.