The latest contestant singing SMILE on 'American Idol' is Thia Megia. Interesting she didn't know this song is the music of Charlie Chaplin's from the 1930s film MODERN TIMES, with lyrics added in the 1950s by John Turner and Geoffrey Parsons. It was first made famous, as a song, by Nat King Cole in 1954.
Thia Megia performance:
The stereo version from the first singer to perform SMILE, Nat King Cole.
More about SMILE at this LINK.