Dawson Casting: Arnold in "Venus and the Man" is supposed to be 16 years old, but the actor is clearly much older.
Handwaved by having his mother say that he's built like "a regular man" despite his youth.
Totally inverted by most of the main cast. Gary Sandy, Loni Anderson, Tim Reid and Jan Smithers all looked their age, but Howard Hessman and Richard Sanders, both of whom could have passed for over 50, were 38 during the first season, and Frank Bonner, also looking somewhere in his fifties, was 36. Gordon Jump, who could have passed for 60, was 46.
The Danza: In the episode "The Americanation of Ivan", character actor Sam Anderson played a local government agent named....Mr Anderson. Also counts as a You Look Familiar as he had previously played the little seen afternoon drive time dj Rex Erhart (or as Johnny calls him 'Rex Airhead') in one earlier episode.
Directed by Cast Member: Frank Bonner directed six episodes, while Howard Hesseman and Gordon Jump directed one episode each.
Keep Circulating the Tapes: As mentioned above, the chances of the show getting a DVD release that isn't butchered beyond recognition due to music licensing snags are slim to none.
With the release of the DVD, Shout! Factory announced that while they were able to get a majority of original music (about 80%), there are some they just couldn't get. Some of the replacement music is close to the original song, such as Pink Floyd's Dog being replaced with a sound alike with Barking Dogs.
The Other Darrin: Mama Carlson was played by Sylvia Sidney in the pilot and Carol Bruce for the remainder of the series, including a reshot scene from the pilot in a Perspective Flip episode.
Permanent Placeholder: The scat closing credits song was going to have lyrics, they just hadn't been written yet, but the producers heard the demo version and liked it just like that.
Referenced by...: An episode with Venus and Johnny drinking on air in a drunk test inspired The Funday Pawpet Show's Herbie to do the infamous "Drunk Show" in which the puppeteers took a shot of Rumplemintz every half hour of the four hour live netcast (and spent the night sleeping it off in the studio).
Screwed by the Network: CBS changed the show's time slot a dozen times in four years, leading to its early cancellation. Although the show was getting decent ratings on Monday nights at 9:30 PM following M*A*S*H, CBS moved it out of that slot as they wanted to free it up for House Calls, which starred former M*A*S*H regular Wayne Rogers, and they also felt that the rock n' roll music and the sex appeal of Loni Anderson were better-suited to an earlier slot, which at that time was thought of as mostly aimed at young people. During the third and fourth seasons, CBS continued to move the show around repeatedly, so much so that cast and crew members claimed that even they didn't know when the show aired. This time slot shuffling hurt the show's ratings and it was eventually canceled in 1982. It probably didn't help matters, however, that MTM co-founder and president Grant Tinker had left the company to become chairman and CEO of NBC the year before.
Spiritual Adaptation: The show's premise and characters are very similar to those of the 1978 comedy film FM.
Throw It In: Richard Sanders, who played Les Nessman, was injured prior to shooting the pilot and had to wear a bandage on his face. It was quickly decided that this would be the character's trademark, so he's always seen with a bandage on some part of his body in subsequent episodes (later explained that it was due to a large, unseen dog that Les owned).
Unfinished Episode: It was going to have a 5th season Story Arc where it's harder to stay a top rated radio station than to become one, but the show was cancelled after season 4.