Photos: See how "The Sound of Music" cast compares to the real life von Trapps

Their lives were subject of one of the greatest films ever made, but it's still hard to believe that "The Sound of Music's" von Trapp family were real life people.

ABC's Diane Sawyer will be revisiting the roots of the iconic musical film, now celebrating its 50th anniversary, in the "20/20" special, "The Untold Story of 'The Sound of Music.'" But you can see how Julie Andrews, Christopher Plummer and the rest of film's cast sized up to their real life von Trapp counterparts in the gallery above.

"The Untold Story of 'The Sound of Music,'" a Diane Sawyer "20/20" special, airs Wednesday, March 18, at 10:00 p.m. ET | 9:00 p.m. CT.