Looking for Mr. Goodbart is the nineteenth episode of Season 28.
Bart gets in trouble on Grandparents Day at school and is forced to hang out with Skinner's mother as punishment. After spending time with various grandmothers in the neighborhood, he learns the benefits of hanging out with the elderly citizens, but eventually recognizes the dangers about taking advantage of them. Meanwhile, Peekimon Get has taken over the town of Springfield.
The episode begins with Bart serving an elderly woman at a restaurant table, showing his mannerism. He then starts narrating to the audience about his story.
Two months earlier, on Grandparents Day at Springfield Elementary School, Bart muddles the lyrics to the song for the grandparents visiting (Grandpa, Grandma), and Skinner heard this, so he takes the underachiever to detention due to how bad and tangled up Bart's lyrics were. But Abraham Simpson II says that he is strong to punish a little boy, but he will be scared to punish a veteran. Skinner, hearing what Grampa said, makes him write "I just wrote one and I'm already tired" on the chalkboard and pronounces a moan. In his office, Skinner is thinking of a punishment for Bart, but his mother walks in and asks him to walk her to the bus stop. Without any other punishment in mind, Skinner punished Bart to do his task. Later, at the Springfield Nuclear Power Plant, Lenny walks into the reactor core while playing Peekimon Get and catches a Rattata. After getting him out of the core, Homer shows Lenny and Carl that is playing Peekimon Get, too, and (in typical Homer fashion) randomly enters the core. However, the day's work shift just finishes, much to the excitement of Lenny and Carl, and they close the door on Homer, sealing him inside.
Bart walks Agnes through the hallway and they meet and insult Martin and his grandmother. Later, at the bus stop, after thinking about being told by Skinner him not to take Agnes with him, Bart gets on the bus with Agnes to the candy store next to the location she will depart at. Meanwhile, at the Springfield Cemetery, Homer catches Rattlesnitch on Frank Grimes' grave, and does a victory dance, causing other Springfieldians to successfully catch it as well, except for Gil, who failed to catch it (in typical Gil fashion), and Hans Moleman, after crashing his car into a tree (in typical Hans Moleman fashion). Back at 742 Evergreen Terrace, after Homer sees several Peekimon all over Maggie's room from his Peekimon Get app, he lets her borrow his phone, giving her a way to see the monsters in her room, much to Maggie's horror. The Peekimon Get app becomes very popular with all of the citizens of Springfield, as Homer and Jeffery Albertson catch a Peekimon at church (much to Timothy Lovejoy Jr's annoyance), and later tries to catch a skunk thinking it was a Stunkasan, but he doesn't observe that it is a real skunk, gets sprayed by the skunk's spray, and faints promptly.
Later, Marge gives Homer a tomato juice bath to get rid of the stench when Lisa comes into the garage and sees that Homer is playing Peekimon Get, and becomes interested to it. However, Homer randomly chooses to pour vodka into his bath and stirs it with celery, much to Marge's annoyance, thinking that Homer is bathing in alcohol instead of tomato juice. Sometime after he gets cleaned up, the family goes out for a walk (with Homer and Lisa playing Peekimon Get together), and Lisa enters the Kwik-E-Mart, where she observes several Springfieldians playing the game throughout the store (including Ned Flanders who tells Apu that the Peekimon he found looks like Apu's elephant god). Bart begins to take the opportunity of the old women's gifts for keeping them company, but one day, while taking care of the elderly at the Curl Up and Die hair salon, a woman named Phoebe realizes what he is doing, but settles to give him money if he is able to pick her up for four days in a row from the Sunnyday Nursing Home.
Meanwhile, Homer tells Lisa that he found out that he can buy Peekimons with real dollars and, after some hesitation, Lisa agrees, too. The next day, Bart arrives at the nursing home and takes Phoebe out in the woods admiring the pleasant nature together. Phoebe reveals that she is a nature photographer, much to Bart's amusement. After spending four days in a row together, she gives Bart the money she promised him, but unfortunately he refuses to take it and Phoebe, having acknowledged that he changed, bequests him her camera and enters the nursing home. Unable to discover the meaning of bequestioning, Bart goes to the library for help and finds out that it means to give an item away when someone passes on and discovers that she could be ill, much to his surprise. Arriving at the nursing home, Bart finds out from two flashbacks of himself and Phoebe that she was using Bart to make an escape.
Bart appears by Homer and Lisa, who are using cheat codes for the game, and asks them to get help in finding Phoebe, so they arrive at the lake Phoebe and Bart used to go to. There, they ask other people who play Peekimon Get to help them locate her, and they accept. While the others are looking for Phoebe, Homer and Lisa imagine they are in the actual Peekimon Get app (with Pokémon-esque versions of them, even Maggie, playing the game) while they sing a parody to the tune of the Pokémon theme. Afterwards, Homer thinks he found something, but it turns out to be an owl that attacks him. Jeremy Freedman finds Phoebe, and Bart thinks she is dead, but she is still alive, telling Bart that she was out alone in the woods, which makes her relaxed and calm. So, Bart brings her back, with him revealing (in narration) that he learned his lesson about playing with women's hearts and taking advantage of the elderly. It turns out that Bart was telling Grampa the entire story at the Springfield Retirement Castle. That night, when Homer and Marge are in bed, Marge tells Homer that she realized about the 600 dollars spent on Peekimon Get cheat codes and Homer tells her that he is sure that it will fade away soon.
Before the closing credits roll at Luigi's, Skinner is having dinner with his date, but Agnes arrives, accompanied by Milhouse, and they start making fun of them. During the end credits, Homer, Lisa, Horatio McCallister and Jasper Beardly sing a reprise of Homer and Lisa's Peekimon Get song from earlier.