Comedian Will Ferrell, dressed up in hippie garb and his wife, Swedish actress Viveca Paulin, joined O'Brien on stage to perform Lynyrd Skynyrd's 1973 hit "Free Bird" as the credits rolled.

Though the actor's voice was a little flat, he was buoyed by the likes of Beck Hansen and ZZ Top, not to mention O'Brien, an amateur guitar player.

The show's musical theme was set earlier in the show when Neil Young performed his 1976 song "Long May You Run."