Undoubtedly, the best part of being Jimmy Fallon is that he gets the opportunity to sing with so many of his heroes (or simply impersonate them). Last night (March 20), he fulfilled another lifelong dream when Billy Joel stopped by 'The Tonight Show.'

In addition to joining Joel's band for an exuberant show-closing rendition of 'You May Be Right,' the two collaborated on the Tokens' 'The Lion Sleeps Tonight.' The duo recreated the original's four-part harmony with the help of an iPad app that allowed them to loop their voices and replicate a doo-wop group standing over a flaming garbage can in the Bronx in 1956. Then, over the background, they traded lead vocals.

As they recounted during the interview portion, the performance had its origins backstage before a recent Billy Joel concert, when Joel, Fallon and Fallon's father bonded over their love of doo-wop and began harmonizing on their favorite songs. They were having so much fun that Joel wound up taking the stage late.