Even though viewers would ultimately embrace the hotly anticipated finale of “Mad Men,” series creator Matt Weiner confessed that he was plagued by increasingly gnawing worries over how they would react.

“I had a ton of doubts,” Weiner revealed during the panel at the Writers Guild Foundation event “Inside the Writers Room with Mad Men,” where he was joined onstage by nearly all of the final season’s writing staff. Admitting that he’d spent the show’s final weeks “in my house covering my face,” Weiner struggled with his confidence. “I just didn’t know. I didn’t want to end the show in an argument. You know, you can’t defend yourself.”

Fortunately, his mental hand wringing was alleviated immediately, he recounted, as he watched the finale with the cast, crew and about 1,600 strangers in a screening at the Ace Hotel. “I had an amazing experience, in that I knew I would not need to go online no matter what was written because I felt everybody kind of emotionally react to the end of the show,” Weiner said, “And you don’t get that much in TV because people are watching it alone in their house. It was a big life moment.”

“The fact is that I think they got it,” said Weiner. “And they totally understand it, and they may not be able to express it in words, and isn’t that cool?” The “cherry on the sundae,” he added, was that in the year since the show wrapped production, everyone involved managed to keep the finale’s plot points secret – including the big Coca-Cola ad reveal.

His anxiety about the reaction to his work was not exclusive to the finale, Weiner admitted. “I go though the same process every time: I have an idea; I think it’s great; I show it to everybody [on staff]; I doubt it as I’m watching them listen to it; and then we’re about to do it and I’m like ‘I don’t know if I want to do it,’ and they’re like ‘No, it was great.’ And then I moved out of my office in December and I spent basically the next six months with my confidence in everything we did slowly eroding.”

But he also knew that was par for the course for his series. “The show has thrived on very high-risk situations, writing-wise,” he explained. “We’ve taken a lot of risks that are contrary to the wisdom of television, including making permanent changes in the cast and changing our sets and committing to big things that aren’t necessarily things that people have seen before, which is always ‘bad.’ As my boss at one job said to me ‘I don’t know if that’s funny – I’ve never heard it before.'”

During the freewheeling panel moderated by “The Simpsons” creator Matt Groening, whose father worked in ’60s-era advertising, Weiner was joined by final season writing staffers Janet Leahy, Erin Levy, Tom Smuts, Lisa Albert, Robert Towne, Josh Weltman, Jonathan Igla and Carly Wray (fellow seventh season scribes Semi Chellas and Bob Levinson could not attend due to other commitments).

“I feel very lucky that I was exposed to people who were super-opinionated and had different points of view,” said Weiner. “And I am very malleable, despite whatever my reputation is, to new ideas, and I always felt that the best part of this job…was that someone would think of something and if it was outrageous or ridiculous or risky or something like that, we would do it. And I’m proud of that.”

Amid the writers’ selections of favorite scenes and conversations about the writers’ room dynamic, the series’ attention to detail, its handling of feminist issues and polarizing characters like Betty Draper Francis and Pete Campbell, much of the discussion centered around the finale, with Weiner revealing some intriguing tidbits:

— The Big Sur encounter group retreat where Don Draper has his epiphany was indeed modeled after the Esalen Institute (which Groening revealed he’d once attended himself). “I never wanted to say it was Esalen,” revealed Weiner, “but we shot it at a house in Anderson Canyon, which is exactly ten miles north of Esalen. And I was trying to find a place [in Los Angeles] because it costs more money and I didn’t want to have another fight with Lionsgate about the very last episode of the show. I just thought it added to it, this idea that Don would be skeptical – he’s a fish out of water; it’s a comic situation, really – and then just the idea that he would reach out to another person.”

— Actor Evan Arnold, who played Leonard, the unloved man whose emotional crisis moves Don to embrace him, was the first person to read for the role during an extensive search, and was so good at the final table read that the series regulars sat up and took notice. “The other actors, they’re kind of melancholy but they’re joking around – it’s senior year,” recalled Weiner. “But they’re the most competitive people in the world, way more competitive than writers, And they’re all sitting there, like ‘Who the f--k is that?’ ‘What? I didn’t know we were really acting. Can I do my thing again?'”

— Weiner pitched Leonard’s heartbreaking speech nearly word for word in the writers room. “This is an easy thing for me to access,” he laughed. “Everyone asks, ‘What character do you identify [most] with in the show? Is it Peggy? Is it Pete? Don? Roger?’ And I’m like, ‘It’s Leonard.'”

— Don’s final fate had been percolating in Weiner’s head since around Season Three. “[I told AMC] ‘It’s going to end with him in an ashram or something in a lotus position – that’s where it’s headed,” he revealed. “It’s 1970. This whole decade, for anybody of any age, is going to be the realization of the opportunity for change, social change, the rejection of that change, Richard Nixon – Napoleon comes in at the end of the French Revolution – and then a turning inward.”

— The iconic real-life Coca-Cola campaign “came to me about four years ago,” he explained. “I was in my office, thinking about an ending because I was in the middle of a negotiation and I didn’t know if I was going to get to end it…I did the Ohm in my head, and then I heard the song. And I was like ‘Oh, of course – that’s the ’70s. It’s a co-option, but it’s pure.’ And I don’t want to have to explain any more than that, but I liked the poetry of it.”