'Little House on the Prairie' child star says set was like 'Mad Men': 'Cigarettes and glasses of gin'

It’s been 50 years since "Nasty Nellie" headed to the prairie.

The surviving cast of "Little House on the Prairie" is celebrating its milestone anniversary at a festival being held this weekend at Big Sky Ranch in Simi Valley, California. It’s where the show was filmed during its nine-season run from 1974 to 1982.

"If you would have told us 50 years ago that this show would remain timeless, we would have thought you were crazy," Alison Arngrim, who played mean girl Nellie Oleson, told Fox News Digital.

'LITTLE HOUSE ON THE PRAIRIE' SAVED 'NASTY NELLIE' ALISON ARNGRIM FROM PAINFUL CHILDHOOD: 'I DID FIND MY WAY'

"We had no concept that this show would still be airing on television 50 years later," she shared. "We didn’t even know if there would still be TV in 50 years! We were stunned that this show became a hit."

The Michael Landon-led series chronicled the adventures of the Ingalls family in the 19th-century Midwest. Despite its wholesome storytelling, life was different on set, the former child star insisted.

"It was the ‘70s," she chuckled. "People drank, people smoked. [Landon] did all of these things. It was kind of strange you’re… on set and people are standing around with cigarettes and glasses of gin. It seemed odd, but that was TV in the ‘70s. It was like ‘Mad Men.’ [Landon] was so not Pa. But then, if you think about it, what a brilliant performance. Here was this man who came to work in his unbuttoned shirt, in his gold chains, in his Ferrari with his Marlboros, and then he turned into Pa Ingalls in a matter of minutes."

Landon, who played patriarch Charles Ingalls, died at age 54 from pancreatic cancer in 1991. The actress described her late co-star as a straight shooter who smoked furiously and battled insecurities when cameras stopped rolling.

"Michael in many ways was a Hollywood person," the 62-year-old explained. "Yes, he owned a Ferrari. He had fast cars. But… the show was therapy for people. And I believe it was therapy for Michael in a lot of ways… [What surprised me] was that… insecurity, because he was so powerful. He was the executive director. He was the producer. He was the writer and star of the show. He was everything. He was loved by millions, absolutely gorgeous, very much in charge… He’d be cracking jokes. He had a wonderfully twisted, warped sense of humor. He was hilarious."

"But you could see that there were moments when he was trying so hard, ‘Will this be good enough?’" Arngrim continued. "He wanted it to be good enough to be perfect. And you could see that there were times when he’d get that look like, ‘Oh, my God, maybe this isn’t going to be perfect.’ And I think that was maybe the thing that drove him, maybe scared him. That it wouldn’t be perfect."

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Decades later, Arngrim still views the beloved patriarch as "complicated and fascinating."

"That was the most fun you could have on a set without getting arrested," she said. "[He was all about] the jokes, the foolishness, always wanting to make the kids laugh… and then being very supportive and respectful at the same time. And then being an absolute task master… all at the same time, all day long. I don’t think I’ve met anybody [else] quite like him."

According to the star, the pilot episode for "Little House" came out in March 1974. It wouldn’t be until September of that year that the series had its premiere.

Arngrim said that unlike everyone else on set, Landon "always knew" that "Little House" would stand the test of time.

"He told [co-star] Melissa Gilbert… ‘Long after we are all gone, they’ll still be watching this,’" she said. "And everyone he said it to shook their heads and smiled, nodded and went, ‘He’s crazy.’ No one believed him. Everyone said, ‘Oh, isn’t that sweet? He clearly lost his mind.’ No one thought this thing would be going 50 years later… We are dumbfounded. We are thrilled. We’re so grateful."

Landon isn’t the only missing star whose presence will be felt this weekend.

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Arngrim was close friends with Steve Tracy, who played her on-screen husband, Percival Dalton. The actor died in 1986 at age 34.

"He was a wonderful person, so funny and incredible," she shared. "He was older than me and treated me with respect. He didn’t go, ‘This dumb 17-year-old.’ He recognized that I had improv skills. So the comedic stuff that we did as Nellie and Percival, we were able to do that. We had a wonderful relationship and became great friends."

"He got diagnosed with AIDS… there weren’t drugs for this," she reflected. "There was no cocktail. They didn’t know what the heck they were doing yet. People didn’t live for years with AIDS. People lived for months back then. So when he went public in 1986 and told everybody he had AIDS, it was devastating to all of us… Back then, if you lived nine months, it was a miracle."

According to the actress, Tracy lived for a couple of years after his diagnosis. During that time, he underwent a grueling experimental treatment. Arngrim thought it would save his life.

"It was very unpleasant, the shots," she said. "It was painful. It was like chemotherapy. It was awful. I said, ‘Is this painful?’ He said, ‘Oh, yeah.’ I said, ‘Well, is it going to work?’ And he said, ‘No. It’s too late. It’s too late for me. It’s progressed too far.’ I said, ‘What?’ He said, ‘I’m just hoping that if I do this, they can save someone after I’m gone.’"

"That’s the kind of person Steve Tracy was," said Arngrim, fighting back tears. "He was absolutely my friend. That’s why I started volunteering for the AIDS Project in Los Angeles and worked with multiple AIDS organizations all through the ‘80s, ‘90s. I wanted to help people, just like him."

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The remaining cast has maintained a close bond over the years. During the coronavirus pandemic, Arngrim hosted live readings of the "Little House" books for fans.

She’s just as busy as ever. The star boasted she has bookings through November of this year, when she’ll reconnect with fans both across the country and internationally.

"The ‘Little House’ books came at the height of the Great Depression, and the series premiered when we were having a terrible recession and people couldn’t afford things," Arngrim said. "And when times got hard in 2020, people turned to ‘Little House’ for comfort. People started making their own bread and all of a sudden, everyone was an Ingalls."

"There’s a deep connection people have to the show, and it’s truly amazing," she noted. "It really has stood the test of time, just as Michael Landon predicted. When times get hard, there’s always ‘Little House on the Prairie.’"