All's Fair in Oven War is the second episode of Season 16.
A two-year remodeling of the kitchen (which (a) results in nobody, including Maggie, looking any older two years into the future, and (b) doesn't exist in any other episodes) leads Marge to make a dessert for a church event which is so popular that Apu suggests she enter the Ovenfresh Bake-off, but when the other contestants sabotage her entry, she returns the favor by adding an extra ingredient to the other entries - Maggie's ear drops, absolutely unaware that Lisa saw her do it; when Bart finds the Playdude magazines that Marge found, cut out all of the nudes, and threw out, he and Milhouse think they should start behaving like the bachelors in the magazines, including turning the treehouse into a bachelor pad, complete with James Caan.
Marge and Homer attend an open house when the house next door is put up for sale. Marge falls in love with the large extensive kitchen. Back at home, Marge asks Homer for a new kitchen. Homer agrees and attempts the renovation himself.
While demolishing the kitchen, Homer unearths his old collection of Playdude magazines. He innocently tells Marge that he kept them only for the articles, and she responds by cutting out all of the nudes from the magazines. Now that they are useless, Homer throws them away, but they are discovered by Bart and Milhouse. They read the articles and are greatly inspired. With the use of these 70s-era magazines as a model, Bart plans to renovate the treehouse.
After Homer's remodeling makes the kitchen useless, Marge hires a contractor to complete the job. The dishes that come out of Marge's new kitchen get great reviews and, on Apu's suggestion, she decides to enter the Ovenfresh Bakeoff with her Dessert Dogs, which are cakes that are shaped like hot dogs.
At the bakeoff, Marge encounters stiff and ruthless competition where some of the chefs mock her and sabotage her cooking, and even that her Dessert Dogs almost ruined by the end of the time limit. So, she barely manages to make them presentable and get them to the room where the entries have to be stored. Still fuming about the behavior of the other chefs, she stoops to their level and resorts to cheating to get even by spiking the other entries with Maggie's ear medicine, much to Lisa's dismay who has seen Marge doing it.
Meanwhile, Chief Wiggum and other concerned parents talk with Homer about Bart spreading the Playdude philosophy to the other children. Homer has a talk with Bart about the true facts of life, which a horrified Bart quickly spreads to the other children, who are just as horrified. Homer solemnly says it was better to tell them now than wait until Bart was old enough to cope.
Marge's cheating gets her to the finals, and Lisa confronts her in the kitchen. Marge retorts by saying that the other chefs deserved it for the way they treated her, and Lisa urges her to do the right thing. In the finals for the bakeoff against Brandine (who has made something which Marge could easily beat without cheating), Marge admits to her foul play and Lisa's faith in her mother is restored. Brandine wins by default and collects the prize from James Caan.
Later, at the Kwik-E-Mart, the Simpsons see Cletus, who is outraged that Brandine has left him for Caan, but he tells them not to worry and swears he will get her back. As James and Brandine drive towards a tollbooth, Brandine runs for cover as a team of hillbillies ambush the car and gun Caan down.