"Home Sweet Homediddly-Dum-Doodily" is the third episode of Season 7.
After a series of misadventures, the Simpson children are put in the custody of Ned and Maude Flanders. Learning that none of the kids have been baptized, Ned sets up a baptism - which Homer and Marge thwart just in time.
Homer gives Marge a surprise trip to a relaxation center. Despite Marge's warning for them to clean up the mess and give the children fresh clothing before they leave, Homer refuses and willingly abandons their children under the ineffective care of Grampa. Meanwhile, Bart has gotten lice from Milhouse's monkey, forcing him to have his clothes burned by Groundskeeper Willie. Meanwhile, Lisa gets her prescription shoes stolen by bullies and hung up on telephone wires. They come home wearing bags, finding out that their parents are not home, and the Child Welfare Agency (prompted by Principal Skinner, who had called them in concern for Bart and Lisa's welfare) has taken offense at the poor conditions of the house (the household chores were simply postponed, but the agency misinterprets such signals as a stack of 20-year-old newspapers obtained for Lisa's history project, and Grampa is sleeping on the family couch). However, as soon as Homer and Marge arrive home, the agents take Bart, Lisa, and Maggie away from their house, as they convinced Marge and Homer to be bad parents.
The Simpson children are taken to a foster home - which is right next door at the house of Ned Flanders. The kids have to deal with Flanders' style nachos (cucumbers with cottage cheese), bedtime when there's still light, and hours of Bible Bombardment. Bart and Lisa hate it, but Maggie enjoys being there, not just because she's a baby, but also because the Flanderses pay more attention to her than Homer did. Ned allows Bart and Lisa to watch The Itchy & Scratchy Show just one time. However, the violent nature of the show as well as Rod and Todd's discomfort makes Ned ban Bart and Lisa from watching it to their further detest.
Being left alone with Homer and Grampa, Marge scolds Homer for not letting her clean up the house and leaving Bart, Lisa and Maggie filthy under his father. She claims that he at least should've let her call her sisters, Patty and Selma, to watch them more effectively and help clean up the house. Homer tries to defend himself, claiming that he didn't want her calling her sisters to care for their children, even if they were more effective than Grampa. However, Marge tells him that she doesn't want to hear any more of his excuses, because this is the last time that she lets him talk her into pleasuring herself over their children's welfare. She runs inside the Flanders house in despair, while Homer is feeling guilty over hurting her. He then berates Grampa for not getting alerted earlier about the Child Welfare Agency that could have given them time to arrive home and clean up the house. Grampa claims that Homer complains at him too much and tells him that he can deal with his own problems. He heads back to the retirement home he lives at, while Homer stews in anger and decides that he and Marge must plead their case in court. At the Springfield County Court House, they plead their case to get their children back (although Homer initially claims she has the wrong family when she names one of the children as "Margaret" until Marge reminds him that she's Maggie). However, a judge, presiding over the case, tells Homer and Marge that in order to get their children back, they must attend a Family Care Class and prove that they are fit parents. When Homer tries to interrupt her, Marge warns him against it because they don't want to add a contempt of court charge to their precarious situation and make Child Welfare more convinced that they are terrible parents.
When Ned finds out from Lisa that none of the Simpson children were baptized because of Homer's lack of belief in God and didn't believe that baptism is necessary, he faints and calls on Reverend Lovejoy for advice. Convinced that Homer was a terrible father, Ned takes it upon himself to give the kids a proper baptism, much to Bart and Lisa's fears.
Meanwhile, since there's no way for Homer and Marge to talk to their children (even by phone), Bart and Lisa help them out by using a newspaper-editing machine that Rod and Todd has and lets Homer and Marge know how much they miss being Simpsons. With a sense of newfound hope, they take classes to become better parents as they are forced to attend a basic class on home care, including such lessons as putting garbage into garbage cans, and leaving milk either in a refrigerator or in a cool, wet sack. While Homer learns well, Marge is genuinely humiliated and Goodman is concerned that she is struggling. Pulling her outside of the Family Care Course, he and another teacher asks her what's wrong. Marge admits that she finds both the class and Homer's actions humiliating. She reveals the whole story of what happened when she came home to discover that her kids were dirty. This was evident earlier in Homer's behavior when they left for their spa date by leaving the house along with Bart, Lisa and Maggie in the lack of care of Grampa, rather than letting her call her sisters to help watch them or let her tidy up the house before they left. She realizes the consequences it had that lead to both her and Homer losing their children in the first place. She tells Goodman that she loves Bart, Lisa and Maggie so much that she will do what is necessary to get them back. He understands Marge's plight, but Goodman reveals that he is doing this not to humiliate her, but also teach her and Homer to become better parents. Although she presumably fails the class, it was revealed that there was a marginal error between the scores and Marge actually passed. Eventually, she and Homer are declared fit parents.
When they go to pick up the kids, they see only a note saying "Gone Baptizin'". They quickly head for the Springfield River, where Ned is about to baptize Bart. Homer arrives at the scene right when Ned is about to sprinkle holy water over Bart's head (baptism as practiced by Protestant and Evangelical congregations tend not to involve the use of holy water at all). Homer pulls Bart over and the holy water falls upon Homer's head instead, baptizing (or burning) him. Homer has a moment of grace after his baptism and confuses Ned. He quickly reverts to his old self and angrily reclaims his kids from the Flanders family. Nevertheless, Maggie would rather stay with the Flanders family than with Homer, Bart and Lisa, until Marge shows up. Her reluctance disappears when Marge arrives in the sunset to pick her up and resumes being a loving mother to her. The Simpson family is back together again, and they head home together, mocking the old paint cans in Ned's garage. Homer and Marge apologize to Bart and Lisa for what happened and promises that Grampa will never again babysit them.