When they got to Princess Peach's Castle, Bowser attacked and Mario fought him in a super easy battle. However, then Peach started yelling at everybody, which caused a huge explosion. After this, Cackletta and Fawful the Awful came and stole Birdo's voice, and, for no real reason, this affected Peach. Mario and Luigi followed Fawful and battled him, but he defeated them with the Mustard of Doom.
They were stranded in Stardust Fields and were supposed to be trapped there, however, George W. Bush did not do a good job guarding the border line, and the Mario Bros. escaped. Then, Bowser was flying by in his Koopa Cruiser and saw them hitch-hiking. He thought that they were hitchhikers and let them on. Luigi had lost all his clothes when they crashed and only had a dress—after this, Cackletta decided to kidnap Luigi, thinking he was Peach. What a mess!
Mario ended up reunited with Luigi, and then they went to the town, where the Queen Bean got hungry and turned into a monster. To make her stop, the Mario Bros. had to get her some pie, however, they got lost and ended up in Chuckle-Burp Woods, where they encountered Popple, and his Rookie who looks suspiciously like Bowser. They then find this hard-to-open can of soda; while Mario is trying to open it, Luigi shakes it up, so the spray propels them back to the Pie Factory, where they find the pecan pie for the queen.
Then the two went to college and defeated Cackletta. After that they met this stuck-up dude named Prince Peasly, who blinded them with his smile. This caused them to go temporarily insane, blow up Some Ship, and land on Islandisland. As they were recovering, Bowser's and Cackletta's bodies fused together by the Washing machine that is convenientently located that fuses/kills people, making Bowletta.
Meanwhile, Toadsworth was supposed to be watching Peach, but he was busy talking to Lady Lima and let her wander into the Sandy Desert, where she got kidnaped every time he stopped looking at her. Too lazy to do anything about this, he hired the Mario Bros. to watch her. But Mario instead decided to go play videogames; he got a high score and won a poison mushroom. He ate it and got a nasty case of Bean Fever, and turned into a bean. Luigi decided to stop Bowletta himself, so he went to her castle, where she had adopted the Koopalings. Bowletta ended up getting hungry and eating Luigi, but, when he was inside Bowletta, he found Bowser who was shoved inside Cackletta's stomach. He pushed Bowser out and then defeated Cackletta. Then everybody was happy, and Peasly gave Bowser to the Koopas as a Christmas present.