Watch two Neil Youngs sing on "Fallon"

For nearly five years, Jimmy Fallon has been impersonating Neil Young with comedic cover songs on late-night television. But on Tuesday, Fallon was joined by the actual Neil Young.

The two Neils sang "Old Man" together, off Young's classic 1972 album "Harvest." Previously, Fallon sang "Fancy" and "Whip My Hair" as the folk/rock icon, but this is the first time he's actually performed a song written by Young. The two are dressed identically, even rocking similar guitars.

Listen to the surprisingly faithful adaptation of "Old Man":