I can't find the vid online, but Will Ferrell played the cowbell with Queens of the Stone Age when he hosted a couple seasons ago. So maybe you were thinking of both performances and got them mixed up? Either way, the QOTSA performance was hilarious. I'd look for that too.
NEW MUSIC TUESDAY ON WEDNESDAY Another one that won't be available on CD until NEXT Tuesday: Rx Bandits - Mandala (The W at Amazon) $8.99 $2.99 DAILY FREE MP3 Monks - Love Came Tumblin' Down (demo) (1965) Coooooooooool