Jimmy Fallon impersonates Bill Cosby to his face [VIDEO]

Bill Cosby stopped by Wednesday night's "extreme sports" version of the Tonight Show with nothing to promote, but he did delight Jimmy Fallon by acting confused and disapproving -- especially when Fallon impersonated him to his face.

"I can't help but talk like you when I talk to you," Fallon said. "'Cause when I talk to you I slow...everything...down."

Later, Fallon asked Cosby to walk a Tonight Show "tightrope," a line of tape on the floor of the studio. Cosby obliged, even when Fallon climbed on his back.