This reminds me of something I had pointed out to me a while back. In the System of a Down song Marmalade, there's a riff that sounds an awful lot like Super Buu's theme in the Dragonball Z dub. They're not identical, maybe 75%? But it's still funny to me. Compare for yourselves: Give 'em time, neither melody comes in immediately.
i think you mean every song ever. there are elements that just sound similar to other songs, because really, it's limited as to what can be done. LOTS CAN BE DONE but it's limited in the end.