In this episode, the Red-baiting Les discovers that his real father was a Communist barber (and that that's why his mother taught him to be obsessed with Communism). This being from the last third of the third season, the final scene is played very downbeat and sad, but the comedy is more solid than in the similarly downbeat "Till Debt Do Us Part," because of the subplots, some of the lines ("I attend all the meetings...") and the presence of ever-reliable Sam Anderson, playing the third of four different characters on the series. Also, after this episode, the show actually dropped the running gag about Les's fear of an imminent Communist invasion -- so he does sort of grow in this episode, at least a little.
Also, since I don't know where else to put this, a 1983 article from TV Guide, long after WKRP had been canceled, had a little glimpse of the behind-the-scenes life on the show. The show did not have many major cast conflicts, but the writers' room was apparently the really messy place:
Rod Daniel, another WKRP producer who has directed episodes of Newhart (both are MTM productions), remembers that "working on WKRP was very chaotic, a combination of energy, anxiety, anger and alcohol, the antithesis of Newhart." [Steve] Kampmann, he contends, "has learned to channel some of the impulses that could be self-destructive, which was a problem for all of us on that show.”
Kampmann thinks self-destructive is too strong a word, but admits that the WKRP group "was like the bad fraternity on campus. On a typical day, you might have found us working hard to meet a script deadline, or engaged in a loud poker game, or in a shouting argument that resulted in a couple of guys crashing through a glass-topped table, or commandeering a security vehicle for a drunken, late-night tour of the studio. But out of that charged atmosphere came a lot of creativity and some very good shows. Nonetheless, "it got to be too much,” and he didn't return the next year.
The security vehicle story was also told by another writer on the show; apparently some of the writers got drunk after a late-night rewrite, stole a security guard's cart and crashed it into a fountain on the MTM lot. And yet of the semi-hit sitcoms that premiered in the 1978-9 season, WKRP probably had the least chaotic set (but only because the others included Taxi and Mork and Mindy).
The music in the first scene is the familiar "Green Onions" by Booker T. and the MGs; I don't know about the song in the tag.
Act 2 and Tag