These famous stars were on the show, in order of appearance:

Tim Reid, Janet Gunn, and also Howard Hesseman, Richard Kline, Charles Nelson Reilly, and Jerry Seinfeld.

Don't forget Michael Des Barres!
(who is probably best known for his role as the most evil villian of all time, Murdoc, on the classic 1980s television show, MacGyver!)

I'm sorry, I spoke too soon. Michael Des Barres was actually a member of the cast!!!! (playing Jack Allen)

But he did star as Murdoc for 7 great episodes of MacGyver! ( and 2 flashback episodes)

And of interest to WKRP fans, he was also on the original WKRP in Cincinnatti (but not as Jack Allen)

He played "Sir Charles 'Dog' Weatherbee" in episode: "Hoodlum Rock" (episode # 1.4) 9 October 1978


In fact, that's the first acting job IMDB.com credits him with!

Didn't Loni Anderson come back as Jennifer once or twice???

jennifer did. she was dating a prince or something?
sigh. Never married, no children.