I remember reading once that Ringo Starr would often bring original songs into Beatles sessions, only to be laughed at mercilessly when they realized he had rewritten some classic Jerry Lee Lewis or Elvis song.
I imagine we all have stories about discovering, to our horror, that our brilliant new composition bears more than a passing resemblance to some other tune bouncing in the recesses of our mind. I'd love to hear some of the forum's more entertaining stories about it.
Back in my late teens/early twenties, I wrote a musical, a sort of Jesus Christ Superstar-style rock opera about John Wilkes Booth and the Lincoln assassination. It started as a 45-minute concept album in high school, then I spent a good chunk of my first year at college writing more songs to fill it out for a stage production. It was a lot of work, so I was trying to crank out material between classes and assignments. I'd demo stuff up in Garageband in my dorm room, then send it to some of my musician friends for feedback.
There was one new piece I was really proud of, a frantic, multi-sectioned group number following the shooting in Ford's Theater. At one point, it turns into a group of Union soldiers interrogating witnesses. I had written it as a sort of escalating call-and-response between the soldiers and the ensemble, with the soldiers' initial statement answered by the crowd on a higher chord tone, with the chord sequence moving upward, i, iii, iv, i.
I sent my demo to the drummer who had worked with me on the concept album, and with barely-contained glee, he wrote back, "Nice rewrite of Smooth Criminal."
It was true: in my haste and excitement, I had completely overlooked the fact that the melody and chord progression of the interrogation section sounded a hell of a lot like Michael Jackson's hit dance-rock song about home invasion. Oops. Out that section went. My drummer didn't let me live that one down for YEARS.