Our heroes visit the Alola TV studios to cheer on Sophocles, who’s competing in a quiz show! Afterward, Rotom bumps into George, the producer of Alolan Detective Laki, who takes them on a tour. Kiawe is beyond excited to see the adorable Magikarp named Karpy live on set—until it evolves into a fearsome Gyarados!
On top of that, the three stars of George’s superhero show get stuck on location and can’t make their shooting schedule. Thinking quickly, he recruits Lillie, Mallow, and Lana to become The Refreshing Trio: Alola Idols! The girls are a big hit, Gyarados gets recast as an intimidating villain, and all’s well that ends well!
The television host announces the beginning of the Alola Pokémon Quiz, with the first to buzz in having the chance to answer the question. Ash and his classmates watch from the audience as Sophocles competes in the show. Noah is also competing and quickly answers the first question correctly, being awarded with a lei of flowers. Sophocles and Noah prove to be an even match, both answering nine questions correctly. The host gives the final question for the preliminary round, and Sophocles eventually loses to Noah.
Backstage, the group comforts Sophocles and Togedemaru after their loss. Rotom then notices George Charino, the producer who works on the television series Alolan Detective Laki. Charino invites the group to see the filming of an upcoming drama, and they all agree. They walk outside and notice a gathering crowd up ahead. Sophocles and his friends make their way to the front of the crowd and are left speechless when they see Karpy. When Ash is confused, his classmates explain that Karpy is a child actor prodigy famous for the hit TV show "Little Magikarp's Melody". Rotom takes some photos before Karpy's manager orders him off the set. The TV crew begins shooting a scene of Karpy's Yungoos friend leaving, but Karpy's voice suddenly becomes too hoarse, and its body eventually starts glowing, prompting Karpy's manager to take it off the set for a rest.
When George is about to leave for a shoot, Rinka and Kenichi run up and inform him that the lead actors from "Fresh-Tree" cannot show up to set because of a Blizzard whipped up by a Froslass and Abomasnow, which is preventing the actors' plane from leaving the Sinnoh region. George then spots Lana, Lillie, and Mallow; and decides that they will star in the show alongside their Pokémon. They all agree, though Lillie is worried about her limited acting experience. George takes the three girls over to the studio for their rehearsals. Meanwhile, the manager returns Karpy to the set and filming resumes. The scene initially goes well, but Karpy suddenly begins glowing again and then evolves into a Gyarados. The manager approaches Karpy and tries to calm it, but it panics upon seeing its new body and flees with the manager, Ash, and his remaining friends in pursuit.
Elsewhere, Meowth and James prepares Jessie, as her alter ego Jessa-Bergère, for an upcoming audition of a drama commemorating the 55th anniversary of Alola TV. In a rehearsal studio nearby, George tells the girls about their starring roles in Thirst-Three, short for The Refreshing Trio: Alola Idols, in which three girls protect the peace of Alola and use their favorite drinks to transform into their superhero selves. He then hands each of them a script, but the trio bungles the superheroes' main catchphrase. George assures them that they did well, and with a little more practice, they will perform better.
As Karpy continues to panic, Ash confronts the manager with some questions, and she admits that she did notice that Karpy's whiskers appeared to be longer recently, but didn't realize that it is part of its evolution process. Karpy charges through Anna's latest shoot, leaving her in a cloud of dust, before entering the Alola TV studio building. Karpy crashes through the filming of an Alola Pokémon Quiz final round episode and interrupts the girls' Thirst-Three rehearsals. Karpy spots George and instantly begins flailing around, and George then realizes that the Gyarados is actually Karpy. George calmly pats Karpy on its head, and reassures it that everything should be fine. He announces that there is still some time for filming and asks for everyone's assistance. George's ingenuity is later showcased in the latest episode of The Refreshing Trio: Alola Idols.
Later, Ash and his classmates gather at Professor Kukui's home to watch Lillie, Lana, and Mallow's acting debuts in The Refreshing Trio: Alola Idols. The episode begins with Mallow rushing to her two friends, played by Lillie and Lana, where the trio is going to be late for class. The three girls notice holes in the main pathway when suddenly, an angry Gyarados, played by Karpy, crashes down in front of them. Gyarados roars at the trio, so the girls decide to take action. Mallow calls over their companions, and Sandy, Shaymin, and Snowy appear carrying drinks for the trio. The girls promptly take a sip and transform into their Alola Refreshing Trio alter-egos in a dazzling display of lights and sparkles, with Mallow wearing pink, Lillie blue, and Lana yellow. The three heroes go on to defeat Gyarados with a powerful rainbow-beamed "Alola Thank You: Sundae Sunrise" attack. The episode ends with the superheroes posing while the narrator asks if they will be able to make it to class on time.
Ash and the other boys are impressed by their friends' performances and congratulate the girls on their great acting. Meanwhile, George announces that Karpy will still have a future in TV as a villain. He and the manager watch as Team Rocket film a scene in which they are fleeing from a rampaging three-headed Gyarados monster. Jessie is annoyed that her Alola debut is so demanding, but Meowth reminds her that she said she was prepared to do anything during her audition. James then questions why he and the others are in the film in the first place.