One time I was listening to classical music because I was in a mood. It was a Mozart piece. The piano player started playing Twinkle, Twinkle, Little Star. At first I was like, "if bro is such a genius, why did he rip off Twinkle, Twinkle, Litt- oh, he wrote it."
I'm pretty sure it was a common folk tune at the time. WA Mozart loved to do "variations on" stuff that people already knew and enjoyed. I don't believe he originated the tune