The two Howards watch the rehearsal from the balcony and later the two versions of Baldwin encounter one another in episode 1x02 "Birds of a Feather".
From episode 5x02 "Unlike a Virgin".
From episode 2x10 "The Abduction".
The Orpheum was used for opening of 'The Chipmunks 2007 World Tour'.
From episode 2x07 "Chuck Versus the Fat Lady".
The lobby of the Orpheum is used with the exterior of the Pantages Theatre.
Source: Tony Hoffarth — Flickr
From episode 3x13 "Waiting in the Wings".