Eddie is moving Joy's treadmill out of their daughter Alison's room. Joy argues that they can't keep Alison's room the same forever. Joy also knows that Eddie is Alison's favorite. Alison walks in the front door, and Eddie hurries downstairs, leaving Joy pinned behind the treadmill. Alison tells her parents that her ski trip with her boyfriend, Ryan, and his family was great. The Woodcocks come in the back door to tell the Starks they returned from their trip. The Woodcocks invite the Starks to a New Year's Eve party.
Alison gets a text message from Ryan. His aunt overheard her making fun of her mustache and Ryan tells her that he has to break up with her. Alison breaks down and runs to Joy. Joy embraces her daughter and grins at Eddie.
Joy tells Eddie about Alison and her talking the night before. She celebrates that their daughter ran to her. Eddie tries to deal with not being Alison's favorite anymore. Alison slowly walks into the kitchen, and Eddie pounces. He quickly forces her out the door for Philly cheese steaks.
At the diner, Alison is still upset about the break-up. The Woodcocks show up to pick up their hoagie for their party and remind the Starks that they're invited. Alison and Eddie talk, and Eddie sees that his daughter has changed. Ryan told Alison that she was too dark and sarcastic, both traits she got from Eddie. Eddie tries to tell her that those traits keep them from being a disgustingly cute couple like the Woodcocks. Alison doesn't care and plans to attend the Woodcocks' party.
Eddie sits in Alison's room, looking over things from Alison's past. He's remembering when his daughter was as bitter as he was. Joy folds Alison's laundry on Alison's bed, and listening to Eddie talk about the time he has left with his daughter. Joy says they should stop trying to keep Alison how she was, and let her be who she wants to be. Joy and Eddie decide to go to the Woodcocks' party.
Eddie and Joy find Alison at the party and tell her that they're done being dark and just want to party. Alison watches her parents, a glint of suspicion in her eye. Eddie shares his resolutions with everyone. He hopes to lose two pounds and look at rainbows. Joy and Eddie really get into the party and do karaoke.
Jeff tells his guests that in Minnesota, they used to dress up like the symbolic old man and baby to celebrate the New Year. Jeff asks who wants to don the diaper, and the room is silent. Eddie looks to his daughter and knows he has to go the extra mile. Eddie steps up.
In the bathroom, Joy fights to get the diaper on Eddie. Joy suddenly leaves Eddie alone, she's unable to handle how she sees Eddie. Alison comes in and tells Eddie that she doesn't need to do this for her. She's horrified and wants Eddie to go back to his dark ways. Alison also realizes that she's not the happy person she's trying to be either. Jeff walks in, furious that Eddie won't wear the diaper. The guests count down to the New Year in the next room.