Liesl admitted she had a crush on Christopher Plummer's Captain von Trapp, and Plummer said he dubbed "The Sound of Music," "The Sound of Mucus," as the entire von Trapp family cast reunited for the first time in 45 years.
In a broadcast of "The Oprah Winfrey Show" on Thursday, the 80-year-old Plummer, who has been reluctant over the years to even talk about the movie, joined Julie Andrews and the seven actors who played the children in the beloved 1965 Oscar-winning film for a session of reminiscing.
"It made my career. It was that big of a movie," said Andrews, 75, who played mischievous nun turned governess Maria. "We had no idea, really, at the beginning, that it was going to be that huge."
Plummer admitted having "fallen in love" with Andrews after seeing her on Broadway in "My Fair Lady" a few years earlier.
The award-winning stage actor who had never before done a group interview with the rest of the cast since the movie was released, said he nicknamed the film "Sound of Mucus" because, "there needed to be a cynic of some kind around to stop it from getting too saccharine."
Plummer recalled that drinking sessions in Austria, in gaps between shooting, had left him too big for his costume as the stern widower who whistles for his children.
"Sixteen Going on Seventeen" character Liesl, played by then 21year-old Charmian Carr, admitted she had a crush on Plummer during the nine-month film shoot. "I had a huge crush on him. He was so perfect, and he spoke with this perfect British accent," she said.
Heather Menzies, who played second eldest daughter Louisa, later posed for Playboy in the 1970s in a bid to shake off her squeaky clean image. "It didn't work," she said.
Thursday's "Oprah" show also featured performances of "Edelweiss" and other songs from the movie by some of the real von Trapp great-grandchildren, who sing at festivals and in concerts around the world.
"The Sound of Music" won five Oscars, including best picture, and its soundtrack with songs like "My Favorite Things" and "Climb Every Mountain" is one of the best-selling soundtracks of all time.
A remastered 45th anniversary DVD and Blu-ray set, including sing-alongs, a map of filming locations, quizzes and a full length documentary, goes on sale on Nov 2.