Photos: Fun with plastic--peripherals that changed gaming

In the heyday of 2D console platformers, Sega pulled out the big guns with Sonic & Knuckles. This special game cartridge had a game slot of its own, which would let you strap on previous titles in the Sonic series. Doing so let you go back and play these original titles with the secondary character, Knuckles, who could go places Sonic couldn't. To accommodate this, the game code was tweaked--adding new items and power-ups that changed the way you could cruise through levels, and allowing players to dust off those old cartridges and play them once more.

This practice might have continued in other games, but the industrywide move to optical media over the next few years (including Sega's follow-up consoles) left little room for the same kind of technology.

Photo by Josh Lowensohn/CNET

Caption by Josh Lowensohn