Adam Levine, master impersonator? The Maroon 5 singer stopped by "The Tonight Show," and engaged Jimmy Fallon in a battle of warring musical impressions. The twist? They both had to sing songs that the performers imitated weren't exactly known for, so prepare for the finest Frank Sinatra version of "Head, Shoulders, Knees and Toes" you could possibly imagine.

 

Nursery songs were the order of the day, but we have to give props to the Roots, too, for coming up with great accompanying music for all the musical styles used here. Is it weird that they've now convinced us that Eddie Vedder really should consider covering "The Muffin Man"?