First, let's try to untangle the issue of this song's title. It appeared on the 1979 LP Joe's Garage, Act I as "Wet T-Shirt Nite." This is the title by which it is still best known and commonly referred to. For the CD reissue, it was altered twice: first in the libretto to "The Wet T-Shirt Contest" and second on the back tray to the more exotic "Fembot in a Wet T-Shirt." The latter seems to reflect Frank Zappa's intention; in an interview, he explained that the "fembot" was the name given to a female robot in an episode of the TV series The Six Million Dollar Man.
"Wet T-Shirt Nite" illustrates Mary's downward moral spiral. After following a rock band as a groupie for a few weeks (she was "the girl stuck to seat 38 on Phydeaux III" -- the name of Zappa's tour bus), she was dumped in Miami. Having no money, she enters a wet T-shirt contest in order to win 50 dollars to get home.
The track is split in two parts. First is the song itself, sung by Ike Willis, a quirky pop tune with a typical odd-rhythm break and cynical lyrics aimed at the Miami bar entertainment scene, so to speak. Then comes the "contest" part, a dialogue between Buddy Jones aka Father Riley, the master of ceremony (Zappa), and Mary (Dale Bozzio), backed by a bar band groove spiced up with funny cues to illustrate the subject discussed. Mary sounds completely disoriented, stupid, and willing to do anything for her 50 dollar bill. Of course, the song shows how music can drive you to low moral standards.
The song "Wet T-Shirt Nite" (the first part) was performed on-stage for a brief period only, in February and March 1979, always followed by "Why Does It Hurt When I Pee?" A live recording appears on the official bootleg Any Way the Wind Blows, but it follows the studio version very faithfully. After an interim period it was replaced by "Joe's Garage."