It is Christmas in Springfield and the Simpson family are decorating the tree. Maggie tries to eat a Christmas ornament, but Bart stops her and gives it to Snowball II. He notices a decoration saying "Todd's First Christmas" and this starts a story narrated by Marge that is set 6 years in the past, beginning with an slightly younger Homer and Marge going to an office meeting at the Springfield Nuclear Power Plant.
Homer promises Marge not to drink, but Lenny and Carl mixes some beer in his soda, making him drunk enough to mock Mr. Burns when the carolers start singing. Burns releases the hounds but they make his ice statue slide all the way to the school, just for Groundskeeper Willie to smash it. Marge invites Homer to leave the party but he asks her to wait until he had filled his pants with shrimp, mayonnaise, and ketchup. She grabs him and they leave on an Uber, but Marge refuse to let Homer inside upon arriving home, leaving him to walk around town with nowhere to go until Ned Flanders lets him join his family as an guest.
Ned's wife Maude is not that happy when the night comes; Homer eats the Christmas ham, uncooked and still in plastic, and has hallucinations of Hell from a painting. Meanwhile, Marge tells 4-year old Bart and 2-year old Lisa that Homer is not coming before Christmas. Maude tells Homer to get out after ruining grace and teaching a younger Rod a bad word and he goes to Moe's Tavern, where Moe walks him home. The only way for Homer to get in the home is through a secret room above the garage that Moe shows him, having rented it in the past to an Irish family. On Christmas Eve, while Homer decorates this room, Bart and Lisa decide to give up all their toys for Christmas if Homer could come back. Marge agrees on the condition that he has to do one thing to show all she has put up with has a point.
Homer hears all this through a vent and thinks of making Christmas cookies as an option, only to burn the kitchen. Just when he needs a miracle, Maude unexpectedly goes into labor, giving Homer the opportunity to make the one thing now being him delivering the baby. Rod informs Maude that Ned is absent, delivering Christmas turkeys to the poor, so Homer proposes to do it while unbeknownst to him, Marge watches from the door. She approaches him and they kiss, fixing their Christmas at the same time Ned comes back. The group decides to name the baby Todd with the middle name being Homer; back in the present, Homer states that Maggie's middle name is Lenny because of similar reasons, surprising her.
In the end, Bart scares Rod and Todd with Grampa's dentures that Grampa was searching for a date night he's having while Homer and Marge make out in the secret room with Moe watching. During the credits, Christmas postcards from various residents in Springfield are seen.