Tōgi Ō: King Colossus is a video game released in 1992 by Sega for the Mega Drive. The game was never localized outside of Japan, however, a fan translation patch was released in 2006 which patches the ROM and makes the game playable in the English language.

King Salmon (キングサーモン?) is a 1992 Sega Genesis/Mega Drive fishing video game that was developed by HOT・B/Sage's Creation and was released by Vic Tokai in North America.

Kirby in Sonic the Hedgehog is a hack of Sonic the Hedgehog by Darkon360. It features Kirby whom replaces Sonic as the lead protagonist. Kirby can inhale most enemies but cannot copy their abilities.

Kirby in Sonic the Hedgehog 2 is a hack of Sonic the Hedgehog 2 by Lone Devil (Also known as Darkon360) for the Sega Genesis/Megadrive. It features Kirby and Waddle Dee whom replaces Sonic and Tails as the lead protagonists. Kirby can inhale monitors and most enemies but cannot copy their abilities. Lives function as health points and the only way to obtain them is grabbing every 50+ Rings, Checkpoints/Lampposts, Randomized 1Up Monitors, or Score every 50000+ points. The hack also features 4 difficulty modes. Hidden Palace is restored but only as a 1 Act Zone for Kirby, located somewhere in Mystic Cave Act 2.

Knuckles in Sonic the Hedgehog is a fan-made ROM of the game Sonic the Hedgehog for the Sega Mega Drive/Genesis, featuring the character Knuckles the Echidna in place of Sonic the Hedgehog, the game's usual protagonist. The history of the game begins with the release of the Mega Drive game Sonic & Knuckles. The unique cartridge featured "Lock-On Technology" and allowed players that also owned the game Sonic the Hedgehog 2 to link the two together and play the game through as Knuckles instead of Sonic. However, partly because of a poorly matching colour palette, no such feature was included in the first Sonic game (instead, attaching Sonic 1 to the Sonic & Knuckles cartridge unlocked the full version of Blue Sphere). In the ROM hacking community, creating a patch that allowed the gamer to play as Knuckles in Sonic the Hedgehog was considered the "Holy Grail of ROM Hacking." On September 1, 2005, Stealth created a hack that allowed a player to do just that. His hack was called Knuckles the Echidna in Sonic the Hedgehog (Knuckles in Sonic 1, or S1K for short) Knuckles in Sonic 1 one gives Knuckles all the moves he has in Sonic and Knuckles, including gliding, wall climbing, and the spin dash. Not only that, Knuckles can transform into his Super form once he obtains all the emeralds (a cheat must first be enabled).