“It is such a spectacular ending, I get chills thinking about it,” Janney said on ‘Jimmy Kimmel Live!’

Allison Janney. Photo: Gilbert Flores/Variety via Getty

Allison Janney is revealing how she reacted to seeing one specific script for The Diplomat.

During an appearance on Jimmy Kimmel Live! on Nov. 4, Janney, 64, explained that when she first read the script for the political thriller’s season 2 finale, she had a visceral reaction. By the time she made it to the end, she did something she had “never” done before.

“I literally threw the script across the room,” the actress admitted. “It was like, ‘What the?’ Because it was such an explosive, such an incredible — everyone has to binge the whole season because I’m only in the last two episodes. It is such a spectacular ending, I get chills thinking about it.”

Janney’s appearance on The Diplomat, although short, got both fans and cast members excited when it was first reported by Variety in January.

She plays Vice President Grace Penn in the series, which follows U.S. Ambassador to the United Kingdom, Kate Wyler (Keri Russell), and her husband Hal Wyler (Rufus Sewell) as they try to prevent a global war.

Allison Janney.Presley Ann/Getty

In October, Russell, who also executive produces The Diplomat, admitted to PEOPLE during a special event for the show at PaleyFest 2024 that she “was nervous, a little bit” when she heard of Janney’s participation in the show.

“Just because she’s awesome and so good,” the Felicity star, 48, said. “I love her. There’s a scene she does in Primary Colors — that movie is so good — where she does this physical comedy fall up the stairs. So I think I was a little nervous, but she’s everything you want her to be. She’s gracious and funny and smart and cool.”

While Russell joked that she “tried to keep it cool at first,” she eventually confessed her love for the film to Janney.

The Diplomat and The West Wing, which Janney starred in, share a showrunner, Debora Cahn. At that same event, Cahn explained to PEOPLE that she didn’t want Janney’s appearance in another political series “to feel like a gimmick,” and she was worried that she wouldn’t be able to create a “distinct” new character for the actress.

Netflix/Courtesy Everett Collection

“A lot of the way that I write, I learned from writing for Allison,” Cahn said. “So there are certain things that I hear that kind of come from her rhythms, So those are in all of these characters. I just didn’t want it to feel like sort of all the same thing.”

Cahn confessed that she then found herself “scared” to write for Janney again.

“I went into a full-on immobilized panic for a number of weeks when the first big Allison episode was coming because it just felt like so much was riding on it and I wanted it to be good,” she revealed. “I wanted it to be good for her and I wanted it to be worthy of these guys in terms of what she brought to the table,” she said in reference to the show’s cast.