Mandy Moore was so taken aback after reading the 'beautiful and upsetting' script for the penultimate episode of 'This Is Us' that it made her 'throw up'

• "This Is Us" star Mandy Moore was sick after reading the script for the second to last episode.
• Moore shared her physical reaction to the "beautiful and upsetting" script during a PaleyFest panel.

"This Is Us" star Mandy Moore had an unexpected reaction to reading the NBC hit's penultimate script.

"The second to last script I sent out to the cast and it made Mandy throw up," series' creator Dan Fogelman told a crowd of fans who erupted in surprise Saturday evening during a panel at PaleyFest LA, a TV festival taking place at the Dolby Theatre in Los Angeles, California from April 2 through April 10.

Insider was in attendance as Fogelman, Moore, Milo Ventimiglia, Jon Huertas, Susan Kelechi Watson, Sterling K. Brown, Justin Hartley, Chrissy Metz, and Chris Sullivan convened for a screening of an upcoming episode of the series followed by a Q&A with the cast to commemorate the series' six-season run.

"It was so beautiful and upsetting that that was my physical reaction," Moore added of reading the script.

"I couldn't breathe," Metz added of her reaction to reading the series' second-to-last script.

The NBC drama, which follows the Pearson family's lives across multiple generations, has become known for making its audience — and cast — a bit emotional.

During the over hour-long panel, moderated by Access Hollywood's Scott Evans, Sullivan, who plays Tobey on the series, challenged that notion.

As fans were screening the series' next episode, set to air on Tuesday, April 5, Sullivan said the cast snuck into the back of the Dolby Theatre to watch some of it with them and listen to their reactions since they usually watch the series alone.

"This show has been pigeon-holed as the sad show and maybe you cried once this episode, but you were laughing your asses off the whole episode," Sullivan said, adding, "I think what happens is we cry once and we forget about all the laughing that we just did."

Later, Fogelman revealed that he finished writing the show's series' finale the night before the panel. Fogelman wrote the series' two final episodes.

The cast said they "all got a text from Dan last night saying, 'Guys, I just finished it."

Fogelman said he has known the show's last moment from the time he started working on the series eight years ago, but he only just wrote it this week.

"It's been a long time coming," Fogelman said, adding that he had just been holding off on writing the series' final words. "I would sometimes talk to the guys and think about what was going to happen in the end and what the end would be."

When Evans asked Fogelman if fans will be satiated with the way the series ends, he said, "I've written it and I feel very confident that we're going to do what you're asking."

Noting that "This Is Us" has been a part of his life for over eight years, Fogelman added that they've taken the responsibility of wrapping up the show "very seriously."

"I wrote the final two episodes. I feel very confident," Fogelman said to a large round of applause.

"This Is Us" airs new episodes Tuesdays on NBC. Eight episodes of the series remain. You can buy tickets for PaleyFest here.