Thanks to a fellow collector for sending me the episode as it aired on CBS.
This episode is most famous for the "Hot Blooded" scene, which Hugh Wilson came up with after hearing "Hot Blooded" on the radio and demonstrating Les's pantomime routine to his staff. It was also the first episode produced with the new "bullpen" set, signalling the show's move (after it came back from hiatus) to a pure ensemble comedy. (This is the first episode that doesn't even try to pretend that Andy is the central character.) Based on the bullpen set, director Asaad Kelada and the actors came up with the famous "walls" gag, which Kelada credited with making the set work, since it gave every character something to do or react to when he came into the room. It was also the first episode written by Richard Sanders (Les) and his writing partner, Michael Fairman.
Cold opening (music: "Shakedown Street" by the Grateful Dead)