George Harrison started the Traveling Wilburys by accident. The European record companies needed an extra song for Cloud Nine. So, he had to make a new one quickly. George enlisted the help of his friends Jeff Lynne and Bob Dylan to expedite the process, and his other pals, Tom Petty and Roy Orbison, came along to watch.
George and Lynne wrote the song, but they needed lyrics. After seeing a box in Dylan’s recording studio that said “Handle With Care,” they wrote the song around that. However, having his friends, each of them expert singer/songwriters themselves, in one place was ultra-rare. It would have been silly for George to pass up an opportunity for all of them to sing on the song. Thus, the Traveling Wilburys was born. Thank god for happy accidents.
Source: cheatsheet.com