Bowser and his minions are working on a mind control serum. Bowser soon reveals that he is planning to turn Toadette against Peach. Meanwhile, Mario, Luigi and their friends are playing baseball, which goes well under Daisy accidentally hits Toadette in the head, causing her to cry very hard. Daisy is ashamed of herself. While Daisy is dwelling on hurting Toadette, she suddenly notices the Koopalings break into Peach's castle, along with a Thwomp and many Goombas. Worse, since she was not watching Toadette, the Goombas take Toadette to Bowser's castle. At one point, a green Toad grabs Iggy's wand and needless to say, Iggy is cursed himself (His right leg becomes black and deformed). Meanwhile, Toadette is finally brainwashed.
Peach and her team are dwelling on what to do next, when suddenly, Rosalina descends into Peach's castle. She is worried about Toadette. After Birdo gets angry with Bowser Jr. for blowing a raspberry at her, Daisy sees a Dry Bones, and Luigi is horrified to see King Boo. Back at Bowser's castle, as the Goombas are cheering, one is knocked into the air. Then, Donkey Kong starts fighting his way towards Bowser, only to get defeated. Wario and Waluigi are impressed, but since Bowser hates them both, he smacks Waluigi and electrocutes Wario. Back outside in a major battle, Luigi dispairs over Peach's loss, but Mario has a plan.
Meanwhile at Bowser's castle, Peach is put in a cage and dispairs over what has happened to Toadette. At Peach's castle, Mario has created a serum to turn Toadette back to Peach's side. Rosalina is unsure, but Mario explains that his demonstrations with many of Bowser's minions were all successful. Mario forbirds fighting Toadette. During battle against Bowser's minions, Bowser insults Rosalina, but Daisy kicks him out of his own castle. Then, Mario meets Toadette. Despite her strong attacks, Mario is able to inject the serum into Toadette. She is happy to see Mario, but Bowser soon arrives and punches Mario in the leg so hard that the bones inside are all shattered. Toadette and Peach rush to Mario's aid, with Luigi and Rosalina watching in disbelief. As Mario is resting, he is shocked to find that his broken leg is also bleeding at the knee.