Kym Karath has always been ready for her close-up.

The actress was just 3 years old when she was scouted while having a cheeseburger at her father’s restaurant in California. It turned out to be her Hollywood calling.

"Some producers walked up to me and my mom and asked my mom if I wanted to be in a movie," the former 1960s child star told Fox News Digital. "And my mother said, ‘You’d better ask her.’ And I said, ‘If it won’t take too much time ‘cause I’m busy. I have a lot of dolls to take care of.' And I guess they were super charmed. And that was the beginning of my first movie, [1963’s] ‘Spencer’s Mountain.’"

Doris Day giving a toddler Kym Karath a bath

Doris Day, left, and a young Kym Karath in a scene from 1963's "The Thrill of It All." (FilmPublicityArchive/United Archives via Getty Images)

The stars of Spencers Mountain looking aghast

"Spencer’s Mountain," a 1963 film starring Maureen O'Hara and Henry Fonda. It was Kym Karath's first film. (LMPC via Getty Images)

However, Karath’s claim to fame was the 1965 Oscar-winning film adaptation of the Rodgers & Hammerstein musical "The Sound of Music." The musical and movie are fictionalized accounts of the real-life von Trapp family who escaped the Nazis in Austria. It told the tale of a 1930s governess who watches over the large family and their widowed father, naval captain Georg von Trapp, with the help of music.

By the time auditions were underway for the film, Karath had already received praise from the press, particularly from Hollywood columnist Louella Parsons. However, she was eager to show off her acting chops.

"By then I was 5 [but] I had an older brother and sister by 15 and 16 years, so… I thought I was 5 going on 18," said Karath. "I was pretty poised, and I walked in with my portfolio under my arm and I said, ‘Good afternoon gentlemen.’… That was the first audition. And then there was a singing audition, which I was more than happy to participate in. And they asked me what songs I wanted to sing. I said, ‘What do you want me to sing?’ Because I knew all of them… I’m a human jukebox to this day… So I sang ’16 Going on 17.’"

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The actors playing members of the Von Trapp family in a promotional portrait for The Sound Of Music,

The actors playing members of the Von Trapp family in a promotional portrait for "The Sound Of Music," directed by Robert Wise, 1965. Left to right: Nicholas Hammond as Friedrich, Kym Karath as Gretl, Angela Cartwright as Brigitta, Julie Andrews as Maria, Christopher Plummer as Captain von Trapp, Charmian Carr as Liesl, Heather Menzies as Louisa, Debbie Turner as Marta and Duane Chase as Kurt. (Silver Screen Collection/Getty Images)

"Kind of ridiculous for a 5-year-old, but as I said, I was 5 going on 18," Karath chuckled.

Karath won filmmakers over, and she was cast as Gretl, the youngest von Trapp. She quickly found herself in Salzburg where the film was set. She described the experience as "spellbinding."

"One of the best things about that movie for me was becoming a family," Karath explained. "And we did become one in real life. And being in Salzburg, Austria, I think, started my profound love of Europe and history. [But] it was not a fun thing missing my father and brother. But my sister and mother were with me. And our group really became a family, which was wonderful."

Robert Wise talks to Julie Andrews and Christopher Plummer behind the scenes

Director Robert Wise is seen here talking with Julie Andrews in between filming "The Sound Of Music." (20th Century-Fox/Getty Images)

"… [Director] Robert Wise was spectacular to work with," she continued. "He was so warm, so lovely and so sweet… It was work, and you needed to remember your lines, but it was easy in a way because I was with my friends all the time."

The film’s leading lady, Julie Andrews, quickly developed a close-knit bond with the child actors. The star, now 87, went on to win a Golden Globe and received an Academy Award nomination for her performance as Maria. Karath described the actress as "a gift."

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Julie Andrews in bed wearing pajamas telling the von trapp children a story

Charmian Carr, who played Liesl, passed away in 2016 at age 73. Her onscreen sister Heather Menzies-Urich, who played Louisa, died at age 68 after she was diagnosed with cancer in 2017. (Getty Images)

"I loved her from the minute I met her," she gushed. "There is never a bad moment with Julie Andrews – never. She’s just the sweetest, most unbelievable, talented, brilliant human… I think we all have the same favorite memory to some extent. That was when she took out her guitar and she just sang to us. And she would have us sing with her in between the scenes to amuse us, to entertain us, to make the time pass. She was a pure delight."

Julie Andrews playing guitar to her children castmates in The Sound of Music

Kym Karath said she quickly bonded with the "delightful" Julie Andrews. (Getty Images)

Christopher Plummer, who starred as the dashing Captain von Trapp, did not offer the same warm and fuzzy feeling to his much younger castmates.

"At the time he was kind of standoffish," Karath admitted. "Very handsome, but I really wasn’t noticing men being handsome at 5 – actually let me correct myself. I noticed that George Chakiris was handsome when he was in ‘West Side Story.’ Our mothers were friends and apparently, I pronounced seeing him in that movie that he would be my husband when I grew up. And I informed my mother that she had to tell his mother for him not to get any older because he had to wait for me."

Kym Karath posing with George Chakiris, both wearing black

Kym Karath with her childhood crush, "West Side Story" star George Chakiris, at The Hollywood Museum. The actor played Bernardo in the 1961 film. (Courtesy of Kym Karath)

"But Christopher Plummer was… kind of forbidding," she shared. "I think he stayed more or less in the role of captain, but he’s absolutely not like that. Many years later… there was an event for 9/11 at the Westport Country Playhouse… I went backstage to see him, and he was waiting for me. Paul Newman was the master of ceremonies. He and [his wife] Joanne Woodward grabbed me backstage and said, ‘Your father’s been pacing the floor, he’s dying to see you!’… Such a lovely man. So courtly, charming and funny. Truly delightful."

Julie Andrews and Christopher Plummer smiling while posing next to each other on the red carpet

Actress Julie Andrews, left, and actor Christopher Plummer attend the Opening Night Gala and screening of ‘The Sound of Music’ during the 2015 TCM Classic Film Festival on March 26, 2015, in Los Angeles. The actor passed away in 2021 at age 91. (Mark Davis/WireImage)

While "The Sound of Music" catapulted Plummer to stardom, he once described the role as "humorless and one-dimensional." He spent the rest of his life referring to the film as "The Sound of Mucus" or "S&M." Still, a GIF of the captain ripping a Nazi flag became a popular meme in recent years, which gave Plummer a new dose of fame.

Christopher Plummer wearing a light blue shirt

Canadian actor Christopher Plummer, circa 1965. (Silver Screen Collection/Getty Images)

The Oscar winner passed away in 2021 at age 91.

Karath said she knew the film made a lasting impact when the fan mail started pouring in from all around the globe.

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Julie Andrews and Christopher Plummer are flanked on all sides by their children

Angela Cartwright, who played Brigitta von Trapp, previously told The Associated Press that cast members have gone through ups and downs and births and deaths over the years but "when we all get together, we pick up where we left off." (Getty Images)

"I could not even spell Paraguay and Uruguay when I was 6," she said. "I had fans in Japan – just everywhere. It’s an honor to have been involved with a movie that has touched so many people through the generations in countries all around the world… To this day, someone will tell me a story that just blows my mind completely…. I remember this woman who said, ‘I used to stand in line with my parents to watch ‘The Sound of Music’ when we lived in Russia.’ To this day, my friends’ children and grandchildren are in awe of that movie."

English actress and singer Julie Andrews as the young nun Maria, teaching the von Trapp children to sing

Kym Karath later met the real von Trapp family which inspired the musical and film. (Silver Screen Collection/Getty Images)

The von Trapps settled in Vermont in the early 1940s where they opened a ski lodge in Stowe. Karath later visited the Trapp Family Lodge and paid her respects at Martina’s gravesite, the sibling who inspired her character.

"People don’t always think about the historic framework of ‘Sound of Music,’ but I think about it all the time," she said. "… These were incredibly brave human beings, immigrants, who had little money when they first got to America. They left so much behind. They were really brave. It was an honor to have portrayed someone who was so fascinating, who led such a remarkable life."

Kym Karath putting her arms around Barry Williams while filming The Brady Bunch

Kym Karath later guest starred in several hit TV shows including "The Brady Bunch," "Family Affair" and "The Waltons." (ABC Photo Archives/Disney General Entertainment Content via Getty Images)

However, life was not always whiskers on kittens and warm woolen mittens. Karath said The Hollywood Museum, which she has long supported, has educated her on the many pitfalls fellow child stars have endured. The museum currently has an exhibition on the Motion Picture Mothers, a nonprofit formed as a small social group of women whose children were involved in showbiz. "Leave It to Beaver" star Jerry Mathers’ mother, Marilyn Mathers, serves as president of the organization. The exhibit is open to the public until June 4.

Kym Karath wearing a black and white dress while sitting down in front of a vanity table

Kym Karath is a longtime supporter of The Hollywood Museum, which currently has an exhibition dedicated to Motion Picture Mothers. (The Hollywood Museum)

"The thing that isn’t discussed very often is that being a child actor is actually child labor," she explained. "It’s very glamorous, and it’s often fun, but sometimes it’s not fun and sometimes it’s terrifying. I have friends who ended up being the sole supporter of their families when they were little kids. It’s a lot of pressure. I think I’m fortunate. I had really stable parents."

"… When I hit puberty, and I was quite developed for my age, there were a lot of horrible people who came forward," she continued. "And my parents… were both terrified of what was happening. And they said, ‘No more – just focus on school.’ I was lucky enough to have gone to this wonderful private girls school called Marlborough. And then I went to university and that took me out of that. But going back into it, after I graduated from university, it was casting couch all over again… It was horrible. And I fled."

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Kym Karath filming a scene with Barry Williams in The Brady Bunch

In the later years, Kym Karath, middle in a scene from "The Brady Bunch," focused on motherhood and writing. ( ABC Photo Archives/Disney General Entertainment Content via Getty Images)

"… There was the Lolita predator-type," Karath reflected. "It was pretty bad. And I wasn’t accustomed to that. I worked as a professional for so many years and I had a very positive experience. I would say 98 percent of it was positive. That was not something I was going to do, that I was willing to do, or wanted to experience. And I was pretty vulnerable after losing my dad, who died tragically during my sophomore year. I said, ‘No more of this.’ And I went to Paris. What else would a 24-year-old do?"

France became home for Karath. She pursued modeling before falling in love, getting married and welcoming a son named Eric. She was considering a return to acting when her son, at 3 weeks old, contracted meningitis and suffered a stroke. With no hesitation, she fully immersed herself in motherhood.

"He needed my full attention," she said. "He’s thriving now. He’s doing great. My son has done really well – better than expected by a long shot. But that was not a situation where you could take the eye off the ball for a minute."

Kym Karath embracing her son Eric

Kym Karath, seen here with her son Eric, is a co-founder of the Aurelia Foundation, which aims to improve the lives of people with disabilities while supporting their loved ones. (Courtesy of Kym Karath)

Karath co-founded The Aurelia Foundation, which aims to improve the lives of people with disabilities while providing support to loved ones.

Today, Karath said, "life is wonderful." She wrote a screenplay that’s expected to be filmed in Paris. Karath stressed she has not given up on acting – she is just waiting for the right part.

Kym Karath wearing a black dress with her filmmaker who has his arms around her

"With director Bruce Beresford, who will be directing ‘20 Boulevard,’ the screenplay I wrote," said Kym Karath. (Courtesy of Kym Karath)

Previously in 2022, Karath and her surviving "Sound of Music" castmates honored Andrews at the AFI Life Achievement Award ceremony in Hollywood.

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The cast of the sound of music wearing various shades of black and navy posing together for a photo

From left to right, Debbie Turner, Angela Cartwright, Julie Andrews, Nicholas Hammond, Kym Karath, and Duane Chase attend the "AFI Life Achievement Award: A Tribute to Julie Andrews" at Dolby Theatre on June 9, 2022, in Hollywood, California. (Rodin Eckenroth/Getty Images for AFI)

"It was hard not to get super emotional that day," she said. "It was spectacular to have her honored. We will always be a family."

The Associated Press contributed to this report.