Locking on Sonic 2 allows players to play through that entire game as Knuckles the Echidna , utilizing his unique abilities to find secrets unreachable by Sonic.
Inserting almost any other Genesis cartridge (including the original Sonic 1 ) grants access to thousands of unique "Blue Sphere" special stages. Gameplay and Story Sonic & Knuckles
The most distinctive feature of Sonic & Knuckles is its unique cartridge design. The top of the cartridge features a flip-open slot that allows players to "lock on" other games. Locking on Sonic 2 allows players to play
The game picks up immediately after Sonic 3 . Sonic (or Knuckles) continues the quest to stop Dr. Robotnik from relaunching the Death Egg. Sonic & Knuckles - Sega-16 Sonic & Knuckles