The nearly three-minute clip from The Tonight Show has gotten about 1.1 million views since it was posted on YouTube Friday.
"In a nod to the classic '80s music video, Jimmy performs a haunting rendition of the song 'Hello' with Lionel Richie. Or does he?" said a message accompanying the video.
Throughout the clip, Fallon plays an artist sketching Richie's portrait, while only the recording artist's head is seen performing the love song on a studio work table.
Both men seem to be trying to suppress giggles during their unlikely duet.
At the end of the clip, Richie's head is replaced by a clay scuplture, supposedly created by Fallon, perhaps suggesting Richie was merely a figment of Fallon's imagination.