This is why the biggest M*A*S*H fans call her Margaret, not Hot Lips
Nobody calls her "Hot Lips" in later episodes.
"Look, Hot Lips," Hawkeye says to Major Margaret Houlihan (Loretta Swit), just after she's burst into his tent party in the pilot episode of M*A*S*H, "why don't you stop worrying about Elmer Gantry, grab yourself a partner and give him a dancing physical?" Margaret stamps her feet at the nickname and leaves Hawkeye's tent in a hurry, putting as much space between her and Hawkeye as she can.
From the very beginning of the show, the conflict between the more straight-laced Margaret and the impish natures of characters like Hawkeye and Klinger provided much of the dramedy's comic relief. According to M*A*S*H star Alan Alda, the character of Hot Lips carried over from the book and the movie, where she was meant as a one-note joke.
"In the scripts, she was continued to be called Hot Lips," Alda said, "but she was called Margaret by the characters after the first couple of years. Partly because she wasn’t a one-joke character anymore, partly because Loretta insisted on writers finding out who this person was."
So if you listen carefully on the TV show, you will notice the characters stop saying "Hot Lips" after a certain point and after that, there was suddenly a need for much more dimension, and that meant the Hot Lips character needed to evolve, whether audiences liked the new developments or not. M*A*S*H producer Burt Metcalfe told the Archive of American Television, "Loretta’s character is certainly the most controversial so far as people’s awareness of a change in a character."
Alda credits Swit with convincing writers to add more nuance to the character, "She would have long talks with the writers, and I’m sure she annoyed them at times, because especially if you have a joke that works, you want to keep doing that joke. The trouble is, if you keep doing that joke over and over again, not only does the actor get bored, but I think the audience gets bored. I think everybody was able to work toward the woman that was Margaret Houlihan, instead of the joke that was Hot Lips Houlihan. And I think the show benefited from it. I’m sure it did.”
Metcalfe attributes a lot of the character changes we saw in Margaret Houlihan to Alan Alda, who also wrote and directed episodes, including the sixth season episode "Comrade in Arms." That episode sticks Hawkeye and Margaret out in a combat zone alone, where they discover they have a lot more chemistry bottled up than either character ever realized. It's a steamy moment in the show's history, but most fans would be shocked to know that Alda wanted that moment to come much sooner than the sixth season.
Swit confirmed in an interview with Archive of American Television that executive producer Gene Reynolds said he didn't think the audience was ready for that moment to come any sooner, and she even laughed in hindsight, figuring she wouldn't have been ready for it either, as an actor.
Metcalfe explained why the M*A*S*H cast had a unique task in playing their characters: "It’s human nature that you want to find more facets to the character you’re inhabiting for such a long time. Certainly that was the case in terms of Loretta, who just felt that she couldn’t keep threatening to report these men to the general or the colonel every other show and she needed to find more. A lot of it evolved when Alan had this idea of a two-part episode in which the two of them are trapped out in the middle of nowhere.” Metcalfe continued, "From that time on, it became more difficult for Hot Lips to represent the conflict of the show. … A lot of comedy comes from that kind of conflict.”
Metcalfe described a similar experience he had with M*A*S*H after Swit's frequent scene-sharer Larry Linville (who played Frank Burns) decided to leave the show. Metcalfe said, "It’s very difficult to make actors play the same tone, the same exact nature of a role without allowing them to grow. That’s why Larry Linville left. He said, ‘I’ve done everything I can do with this part and I just can’t do it anymore.’ And he was wonderful in it. And there was no bitterness in it, either on his part or on ours, when he decided that he wanted to leave."
For her part, Swit expressed nothing but admiration for M*A*S*H writers, saying, "The writing was spectacular. … They would write wonderful, wonderful material for her." And by "her," Swit, of course, means Margaret, not "Hot Lips," who was primarily the source of foot stomps and cartoonish outbursts. Swit went on, “It’s so easy to work on good material and real behavior.”
So next time you're talking M*A*S*H, keep in mind that the major prefers to be called the Margaret, not Hot Lips.