Fusion levels are one of the main features of Mushroom Kingdom Fusion. Directly emphasizing the "Fusion" aspect of the game, these are special levels that combine a stage from one game with another stage from a different game, utilizing features, enemies, and gimmicks from both. They can also combine more than two stages together, although rarely. Generally the combined stages will have a number of similarities between them.
What makes a level a Fusion level is that it combines levels from different source games in different series together into a level that you can visually tell is a fusion of two different worlds, often with visible transitions in the tileset between the two game universes. Levels like Green Grove Zone, Fiddler's Green, or Tower of Babel are not Fusion levels, even though they may use tiles and enemies and such from multiple games- those stages are simply combining different parts together to reach a single unique result, rather than trying to emulate a fusion between game universes. Similarly, levels are not Fusion levels if they simply use enemies or music from other games.
Fusion levels can be found in all worlds except for Worlds 2 and 5, usually as optional levels. World 1 has it's own special section set aside for Fusion levels, called "No Man's Land", and World 0 will likely be made up of nothing but Fusion levels. Also, the game's World Exits turn parts of normal World 1 levels into Fusion levels as the player progresses through the game.
List of Fusion levels by World
- World 1-16: Mushroom Forest (Mario/Little Nemo: The Dream Master)
- World 1-17: Storm Canyon (Mario/Rayman/Metroid)
- World 1-18: Isle of Mystery
- World 1-F6: Fortress of Traps (Mario/Castlevania)
- World 1-S10: Foul Fungi
- World 1-S11: The Crossroads
- World 1-S12: Mushroom Hill (Sonic & Knuckles/Super Mario World)
- World 3-6: Skull Man Wastelands (Mega Man 4/Ghosts 'N Goblins)
- World 3-S3: Temple of Uranus (Mega Man V/Mega Man 9)
- World 4-1: Forest of Silence (Demon's Crest/Castlevania)
- World 8-10: Bubble Pipes (Super Mario Bros./Bubble Bobble)
- World 9-7: Infected Station (Halo/Contra)
- World 9-9: Moon Fortress (Ducktales/Megaman)
- World 9-S5: Wart's Nightmare (Super Mario Bros. 2/Halo)
- World -1-4: Abstract Landscape