'Little House on the Prairie' star Alison Arngrim reveals the 'great debt' she owes Sean Penn

The new Discovery+ documentary Citizen Penn, shines a spotlight on Sean Penn's second career as an activist and humanitarian. But the Oscar-winning actor has a long history of helping others. In a recent interview with Alison Arngrim, the Little House on the Prairie star revealed how a teenage Penn came to her aid on the set of the beloved NBC drama... by passing out. "I owe him a great debt," the actress tells Yahoo Entertainment 40 years after her time on Little House ended. (Watch our video interview above.)

Here's the backstory: Although it was set in 19th-century Minnesota, the Little House series was filmed in 20th century Simi Valley — an area of California where temperatures skyrocket during the summer. Arngrim was 12 when she was cast on the show as Nellie Oleson, a role she played for seven seasons, from 1974 to 1981. Along with her fellow child co-stars like Melissa Gilbert and Melissa Sue Anderson, Arngrim had to spend those long, hot days in heavy period garb. "Every summer, I would faint because it was a million degrees where we filmed," she remembers. "I was wearing a dress and petticoats and a wig. It was insanely hot, and I would occasionally pass out."

Arngrim recalls that her regular fainting spells didn't engender much sympathy from the adult cast and crew members. "People were looking at me like I was some kind of wuss," she says. Enter a teenage Sean Penn, whose father, Leo Penn, was one of the industry's most prolific directors of episodic television at the time. The elder Penn had been hired to direct a 1974 episode of Little House, and he seized the opportunity to give his then-14-year-old son his first on-camera appearance. "Sean was brought on set to hang out and be an extra," Arngrim explains. "He had no lines, he was just in the scene."

Penn may not have had any lines in the episode, but he ended up speaking volumes off-camera. At one point during the day, he was overcome by the heat and passed out. "This big teenage boy went down like a sack of potatoes!" Arngrim remembers. "And he didn't get back up again: I always got back up again. He was down for the day." Penn's plight ended up convincing the Little House cast and crew that the heat was a real problem for the young actors like Arngrim. "I was cut a lot of slack [after that]," she says. "They were like, 'Maybe she's not making this up.'"

Penn made one more appearance on Little House in a 1975 episode that his father directed, and then took a break from acting until 1979 when he started booking his own gigs. In 1981 — the same year that Arngrim filmed her final episodes of the series — he landed a big-screen breakout role in the drama, Taps, alongside rising stars Tom Cruise and Timothy Hutton. That movie put Penn on the path to becoming one of the most sought-after actors of his generation, as well as a two-time Oscar winner for 2003's Mystic River and 2008's Milk.

When he's not acting, Penn also oversees the charity organization, CORE, which provides disaster relief to nations like Haiti. And Arngrim says that she's since had the chance to thank her former co-star for the way he assisted her at the beginning of his career. "Years later, I had a chance meeting with Sean and [thanked him]. He was like, 'You're welcome.' So I did get to thank Sean Penn for having the good grace to pass out like a sack of potatoes!"

Little House on the Prairie is currently streaming on Prime Video.

— Video produced by Jen Kucsak and edited by John Santo

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