Sonic & Knuckles was the last Sonic the Hedgehog game released for the Sega Genesis, and also tied together the previous trilogy. The main game brought in Knuckles as a main, playable character with his own unique set of moves, while keeping Sonic fresh on his adventure to beat Dr. Robotnik.

For Sonic, the game play was still the same as his previous games where speed was his biggest element as he would blaze through the levels in no time. Tails was still his trusty sidekick though and able to give him a lift every now and then. It was even easier if you could get a 2nd player to take control of the two-tailed fox. Knuckles was fast, but his advantage was in his ability to glide across the stage, latch onto walls, and bust through rocks that Sonic cannot.

The cartridge could connect with cartidges of the previous 2 Sonic games, and allowed for special features never unlockable before. Having Sonic 2 or 3 attached would allow you to play through the entire game as Knuckles, which was never an option before. Doing so allowed you to explore the game worlds in a way Sonic never could, and made those titles instantly replayable by getting to take control of Knuckles.

Not only Knuckles, but even Tails got a great new chance to shine. Though he wasn't a main playable character in the main game, when attached to Sonic 3 you could take control of just him and soar through the levels as long as his tails could carry him.