Bowser heads to the real world, and Mario and the gang head out to stop him. Along the way, Mario meets his old girlfriend Pauline Fransisco, his parents Claude and Jamie Mario, and his old rival, Foreman Spike, who assist and hinder his ways towards defeating Bowser once and for all.
- Kenton Duty as Mario Mario
- Laura Marano as Peach Toadstool
- Calum Worthy as Luigi Mario
- John Cena as Bowser Koopa
- Jack McBrayer as Bowser Koopa Junior/Waluigi Wario
- John C. Reily as Wario Wario/Foreman Spike
- Bella Thorne as Pauline Fransisco/Jamie Mario
- Ray Romano as Claude Mario
- Sarah Silverman as Yoshi
- Olivia Holt as Gina
- Madison Pettis as Toad/Yvan/Wolley/Toadette
- Mateus Ward as Kamek/Koopa Troopa/Iggy Koopa
- Maile Flanagan as Goomba
- Drake Bell as Lakitu
- Kenton Duty as Ludwig von Koopa
- Jack McBrayer as Lemmy Koopa/Larry Koopa
- John C. Reily as Roy Koopa/Boom-Boom
- Mateus Ward as Iggy Koopa/Pom-Pom
- Laura Marano as Wendy O. Koopa
- Bella Thorne as Ellen D. Koopa
- Madison Pettis as Dolly P. Koopa/Mushroom Kingdom Citizens
- Ray Romano as Morton Koopa Jr.
Bowser is in his castle, sitting on his throne with Princess Peach next to him in a cage. Peach demands that he lets her go, but Bowser refuses. Kamek then runs in and tells Bowser that Mario has arrived. Enraged, Bowser orders Kamek to send out different minions, but they all are either missing or injured. Bowser roars and decides to battle Mario again, but before he can even leave his throne, Mario has entered the room and is now jumping on his head. Bowser is knocked unconscious as Mario frees Peach and flees from Kamek, who realizes his wand is missing.
The intro and opening credits show. Afterwards, it shows a scene with Bowser back on his throne. He now has a black eye, and a large bandage on top of his head. Kamek, Koopa Troopa, Goomba, and Lakitu are by his side. Bowser asks Goomba why he always fails. Goomba replies that Bowser's too unoriginal, which gets him smacked across the room. However, Bowser realizes that he's right and runs off. Goomba is confused; is he in trouble, or is he a genius?
Bowser calls upon Ludwig and Iggy, and has them build him a portal to the real world. With help from their siblings, Ludwig and Iggy get to work. Upon finishing, they call for Bowser and show him. Bowser has already kidnapped Peach and brings his minions (Koopalings, Kamek, Goomba, Koopa Troopa, and Lakitu) through the portal.
Meanwhile, Mario, Luigi, Yoshi, Gina, Yvan, and Wolley are heading down the path towards Bowser's Castle. Luigi finds it odd that none of Bowser's minions were out to stop them, but Mario brushes it off as Luigi worrying too much. Upon arriving in the castle, they find it completely abandoned. Mario searches Bowser's throne room for Peach, while Luigi and the others search the Koopalings' rooms. Yvan finds Toad and Toadette hidden in a corner in Lemmy's room, while Luigi finds the transport in Ludwig's room and falls in. Toad tells Yvan what he knows, which isn't much, but he knows that Ludwig and Iggy were building something. Gina realizes that Luigi's missing and they all head to Ludwig's room to find the transport. Mario decides to leap through, and is followed by Yoshi and Gina. Yvan, Wolley, Toad, and Toadette decide to stay behind.
Mario emerges from the portal in Brooklyn, followed by Yoshi and Gina. Mario and Gina climb onto Yoshi to look for Bowser and Luigi. Luigi, meanwhile, is exploring Brooklyn when Waluigi appears and tackles him. As they fight, Mario hears them and heads dashes over. Yoshi attempts to grab onto Waluigi with his tongue, but discovers his tongue too short. Mario tries to jump on him, but discovers he cannot jump high anymore. Gina throws a punch and knocks Waluigi unconscious. Luigi shoves the purple clone off of him and discusses with Mario, Gina, and Yoshi why they no longer have their powers. Luigi realizes that they're normal humans again in the real world. Yoshi, however, is more like a dinosaur and less like a Yoshi. Waluigi wakes up and Gina pins him, asking why he's here. Waluigi explains that he and Wario found a secret warp pipe leading to a bathtub, and decided to earn some money in the real world. Mario asks where Wario is, but just afterwards, Wario tackles him. Yoshi, Gina, and Luigi battle with Wario and Waluigi until the brothers flee.
Up in the sky, Bowser Jr. is watching the heroes from a Clown Car-like helicopter. He sees them defeat Wario and Waluigi and heads back to Bowser's hideout on an unfinished construction site. Here, he tells his dad that Mario and his team have learned how to fight in the real world. Enraged, but not shown, Bowser orders Lakitu to go battle him. Lakitu, who looks like a turtle riding in a normal cloud, heads out to where Jr. said they were. Peach, meanwhile, uses her crown to try to pick the lock.
Mario and the team follow the Wario Bros. to a large construction site, which Wario climbs while Waluigi continues running. Luigi and Gina, riding on Yoshi, chase after Waluigi while Mario follows Wario. While climbing, oil drums begin to drop, and several blocks block his path. Grabbing a hammer, Mario heads up the large building to find that, on top, is not only Wario but also his old rival Foreman Spike. After a short conversation, Mario, Wario, and Spike begin to battle (with Wario and Spike working together). Mario uses his hammer to attempt to knock Wario unconscious, but Wario kicks Mario and sends him plummeting. Mario hangs on for dear life while Wario and Spike laugh.
Back in the Mushroom Kingdom, the Toads are having trouble running the kingdom on their own. While Wolley and Yvan are trying to answer all of the other Toads' questions, Toadette wonders where Mario is. Toad remembers Stuffwell, who can call Mario at anytime. Rest TBA.