Mario & Sonic 2 is the sequel to the Best Fanon, Mario And Sonic.
Three months since Mario and Sonic have met, their worlds have been in peace. But one day, Bowser and Dr. Eggman team up to get rid of their enemies once and for all. The next day, a big tornado Bowser and Dr. Eggman created damaged Mario's world, and then Sonic's world. Mario and Sonic both know they will have to join together again and defeat their arch rivals. At the Mushroom Kingdom, Mario says goodbye to Peach and visits Professor E. Gadd. For 100 coins, E. Gadd builds a transporter to Sonic's world. There, Mario and Sonic travel around Sonic's world and defeat various bosses, but they never find Dr. Eggman. After Sonic's World is cleared, Mario and Sonic use the transporter to go to Mario's world. There, they travel to Bowser's castle. Mario thinks Bowser and Dr. Eggman are hiding there.
Mario and Sonic travel through Bowser's castle to find Dr. Eggman and him. There, they fight several Goombas, Koopas, Paratroopas, and Paragoombas. After Mario and Sonic defeat a Mega Goomba, they fight Bowser Jr. After they defeat Bowser Jr., he drops a key to Bowser's dungeon. There, Mario and Sonic find Luigi and Tails. Tails says Bowser and Dr. Eggman captured them... and they ARE in the castle. After that, Luigi and Tails join Mario and Sonic. Suddenly, the four heroes find themselves in a large room. A few seconds later, Bowser and Dr. Eggman appear. Mario, Sonic, Luigi, and Tails immedietly attack the two villains. After a long fight, Bowser and Dr. Eggman are finally defeated. Then Mario and Luigi find themselves in front of Peach's castle, and Sonic and Tails find themselves at their world.
- Luigi and Tails become playable at the Bowser's Tricky Dungeon level.
- At the Final Battle level, Mario transforms into Super Mario and Sonic tranforms into Super Sonic.