Beyond the main path, Sonic & Knuckles contains several hidden areas and fun easter eggs:
- Hidden Palace Zone (Sonic 3 & Knuckles): While a main zone in Sonic & Knuckles, its role changes significantly when locked on with Sonic 3. It becomes a central hub for accessing the Super Emeralds.
- Knuckles' Hidden Paths: Knuckles has unique paths in almost every zone, often leading to secret areas, power-ups, or shortcuts that Sonic cannot access. Always explore vertically with Knuckles.
- Sound Test Secrets: The Sound Test menu often holds hidden codes for level select or debug mode, as detailed above. Experiment with different sound combinations.
- 'No Way!' Screen: If you try to lock on a non-Genesis game or a game that doesn't have a specific lock-on function, the game will display a unique 'No Way!' screen with a randomized Blue Sphere stage. This is a fun nod to the game's unique technology.