I didn't know "Don't Cry for me Argentina" was from Evita for a while.
"If this is going to be a Christian nation that doesn't help the poor, either we have to pretend that Jesus was just as selfish as we are, or we've got to acknowledge that He commanded us to love the poor and serve the needy without condition and then admit that we just don't want to do it." -Stephen Colbert
"Have Yourself a Merry Little Christmas" was released in 1943. The movie was released in 1944. Probably written for the show and just released as a teaser for the movie. (same composer & lyricist)
"If He Walked Into My Life," from Mame. When I heard this song being performed in Mame, the first thing I said was, "Wow that's that song I always hear on elevators and in restaurants." It was really a surprise to find it was from a musical.
I always knew those songs were from Sound of Music, but just because I grew up on the movie. I was shown it when I was very little, and I think since then I've been a musical theatre nut.
"Cages or wings, which do you prefer?"-- Tick, Tick...BOOM!
I'm with those who didn't know about One Night in Bangkok. It was a pop hit and all, so until I got into musical theatre I never would have guessed. (It does give the lyrics SO much more meaning now that I know the show.)