The Beatles were originally a skiffle group known as the Quarrymen, they then changed their name to Long John (as in Lennon) and the Silver Beetles, then it was the Silver Beetles, then Just Beatles.
Additionally, on top of Ringo replacing Pete Best as the drummer, originally Stu Sutcliffe was the Bassist for the group a renowned artist around Liverpool, he quit the band to pursue his art in Hamburg, and Paul switched from second guitar to bass. Stu later died from a brain aneurysm just before the group took off, the effects of a bar room beat down in Liverpool.