St. Elsewhere pushed the envelope on September 30, 1987 when Dr. Donald Westphall tendered his resignation by mooning boss, Dr. John Gideon (Ronny Cox), and actor Ed Flanders bared his backside for the most flagrant display of nudity on network television to that date. But it turns out that this was not their first foray into exposed buttocks.
Thank you to a sharp-eyed anonymous commenter who spotted this cheeky detail thrown into the third season's "Girls Just Want To Have Fun", originally aired November 28, 1984. At about eight and a half minutes in, Dr. Mark Craig (William Daniels) is engaged in another conflict with Assistant to the Chief of Services Joan Halloran (Nancy Stafford) when a female extra emerges from a room into the hallway.
Her hospital gown isn't quite fastened all the way, and for a few frames, her bare butt can be seen, tan lines and all:
About five minutes later, bone marrow donor Herschel Millstein (Bill Macy) is explaining to visiting specialist Dr. Christine Holtz (Caroline McWilliams) why there's such bad blood between him and his brother when the brazen blonde makes another appearance:
As the actors exit screen right, the young woman's assets are still on display:
Indeed, girls just want to have fun, sometimes by letting it all hang out.
Here are the clips: