A song you didn't realize was a cover?

Years ago, I used to think this Gladys Knight & The Pips version of "Midnight Train to Georgia" was the original version but later found out that the original version of this song was recorded by Whitney Houston's mother, Cissy Houston. Also, Cissy is the one who suggested changing the title to "Midnight Train to Georgia". The song was originally called "Midnight Plane to Houston". Another one is "Respect". Years ago, I used to think the Aretha Franklin version was the original version. Actually, the original version of "Respect" was recorded by Otis Redding, who wrote the song.