(ABC News) -- Dame Julie Andrews made "Good Morning America" come alive with "The Sound of Music" this morning in honor of the iconic film's 50th anniversary, making a special visit to celebrate and reflect back on the most successful movie musical of all time.
"I think it's a joke. I think someone pulled a fast one on me," Andrews, 79, said of how quickly the time has passed since the film's premier on March 2, 1965. "I lost 20 years somewhere."
There have been many commemorations and tributes to the musical already this year including four books, Lady Gaga's Oscar performance and a special five-disc set being released today, but all that could have changed due to Andrews' early doubts about the role. The British actress nearly turned down the role of Fraulein Maria fearing it was too similar to her Mary Poppins character.
It's a problem she solved however, effectively turning the story of a young governess who wins the hearts of the von Trapp children through song into her second blockbuster hit in less than a year.
"If somebody had said 50 years ago you'll be sitting here one day and it will be 50 years from now, how could you possibly imagine that? You couldn't," Andrews explained half a century after winning the statue for Best Picture.
She believes the film has continued resonating with audiences for so many years because of "obvious" reasons, namely the fact that "every seven years there's a new generation and they get introduced to it, but then the film has to be pretty good to last that long anyway."
"It was one of the perfectly crafted Hollywood movies full of joy and love and family and adventure," Andrews added. "And it's got children and nuns and scenery and beautiful music, so somewhere in there is the secret."
Bumping into the film occasionally is "like an old friend," she said. "The memories are great. The pleasure of making it and the friendship with the children and with Christopher [Plummer] continues, and I see him a lot and the children were always in some contact one way or another."
Andrews revisited many of the film's memories recently, traveling with Diane Sawyer to retrace specific scenes and locations from "The Sound of Music" for an upcoming ABC primetime special, "The Untold Story of The Sound of Music."
"The two of us went back to Austria and we visited the scenes of 'The Sounds of Music,'" Sawyer said on "GMA." "You'll hear the hilarious things that happened there, you'll hear what she was really thinking as she was walking toward Christopher Plummer, I find your mountain and of course 'Do-Re-Mi.'"
"We never stopped giggling and laughing and talking," Andrews recalled.
The two women also visit the real von Trapp home, which was the first time Andrews ever saw the actual estate in person. For the movie, she explained, they created a "slightly bigger house in a more countrified setting."
Sawyer's special, "The Untold Story of 'The Sound of Music,'" airs March 18 at 10 p.m. on ABC.