This Is Us Creator Admits He 'Didn't Have a Backup Plan' for Finale Scenes Filmed 4 Years Ago

The creator of This Is Us is opening up about the flashback scenes involving the younger Big Three that were filmed four years before Tuesday's series finale.

In a recent interview with Entertainment Weekly, creator Dan Fogelman revealed that his crew shot half of the finale episode years ago, when the younger versions of the Big Three — Mackenzie Hancsicsak (Kate), Lonnie Chavis (Randall) and Parker Bates (Kevin) — were still children.

Now Fogelman, 46, is describing why he chose to do film those scenes so early — and what might have happened if the footage, which he didn't revisit until two months ago, didn't work out.

"We shot this episode years ago, primarily to capture [the kids] in a moment of time when it would feel nostalgic to us and to the audience," Fogelman explained at the series finale screening and panel on Sunday. "We shot it at the beginning of season 3, but with the pandemic, it added time."

"I never looked at it, so we shot four or five days worth of material with the kids and Milo [Ventimiglia] and Mandy [Moore], and some of Sterling [K. Brown] and Ron [Cephas Jones] and Eris [Baker] and Faithe [Herman] and then we put it away and never looked at it again," he continued. "Then, about two months ago ... I said to our editors, I was like, 'Guys, I have to look at it now. I have to know before we go any further that it's good and that it's what we want it to be.'"

Maarten de Boer/NBCU Photo Bank/NBCUniversal via Getty Lonnie Chavis as Randall, Mackenzie Hancsicsak as Kate and Parker Bates as Kevin in This Is Us season 2

RELATED: This Is Us Creator Reveals Certain Scenes from the Finale Were Filmed 4 Years Ago

It was only after Fogelman watched the footage back that he felt a sense a relief.

"That was my first moment of my shoulders going down a little bit and relaxing because I saw the footage that existed that we shot three to four years ago, and was like, 'Okay, we have it, it's really good,'" he recalled. "I knew that was gonna be the final shot of the episode. Lonny, watching his father watching the family, and I was like, 'Okay, we have it now,' and that relaxed me."

Though the moment was relieving for Fogelman, he admitted that he was extra grateful it all worked out because he didn't exactly have an alternative plan.

"I didn't have a backup plan, which made it really scary," he told reporters on a conference call Tuesday ahead of the finale. "I felt confident ... I had been there on the days we shot that years ago. [executive producer/director] Ken Olin, and I knew how important it was gonna wind up being, so I felt confident globally it was gonna work."

"I knew how good Mandy and Milo and the kids were gonna be in it," he continued. "It was more that, 'Do I have make slight adjustments?' Not overhaul the entire plan, consider altering the storyline in present day, accommodate for something that's small that might not working in the past."

"I didn't have a big, full-fledged, back-up plan, which is what made it all a little bit terrifying," he added. "It was literally why I had to watch the first cut of the 'past' footage with my wife — which I've never done before — because I was too afraid to watch it alone."

Ron Batzdorff/NBC Milo Ventimiglia as Jack, Mandy Moore as Rebecca

As fans know, the footage — which became a major part of Tuesday's finale — followed the Pearson family as they spent a Saturday afternoon together, playing with chalk and pin the tail on the donkey, watching home videos and Jack teaching a shaving tutorial to Randall and Kevin. It was paired alongside a present day storyline, where the Pearson family gathered for Rebecca's funeral.

"…they grow up so fast, and so 3 years ago, while we were shooting season 4, we began filming tonight's series finale.🤯 Look at these babies!!😍 #ThisIsUs" Moore wrote on Instagram Tuesday, beside photos of the flashback scenes.

Ventimiglia, who plays Jack Pearson, previously told EW that doing the scenes in advance "didn't seem that big" at the time, or "one of those things that you think, 'Wow, this is going to be a massive moment for the show. Thank God Dan was thinking ahead to get it!'"

"[They] just played as any other scene[s] that we shot, which was good," added Ventimiglia, 44. "It kind of took the pressure off. I remember Mandy and I walking off set and Dan going, 'Those were the final shots of the show.' I mean, he said it like it was in stone."

RELATED: This Is Us Creator Unpacks Rebecca's 'Fitting Conclusion' and Her 'Meaningful' Stops on the Train

Fogelman, who wrote the last two episodes, also told EW that the finale was intended to feel "like a time capsule of a family" and "purposefully a little different, in a really good way."

"It is about a special day in the past of this family, and the simple things and the little things, as the adult family buries their mother. It will just be a very simple, quiet episode after a very big, loud one," Fogelman said, referencing the penultimate episode, in which Moore's character Rebecca died.

Added Moore, "I just remember closing [the script] going, 'You stuck the landing, Dan. You really did,'" added Moore, 38. "No one's going to be disappointed. This is a really beautiful way to end this story."