Neil Patrick Harris Sings 'Dream On' on Glee

Neil Patrick Harris' much anticipated guest appearance on Glee Tuesday did not disappoint, as the Broadway vet killed in a duet of Aerosmith's "Dream On." Encore, encore!

Neil Patrick Harris' much anticipated guest appearance on Glee Tuesday did not disappoint, as the Broadway vet killed in a duet of Aerosmith's "Dream On." Encore, encore!