Knuckles the Echidna in Sonic the Hedgehog 2 (Genesis/Mega Drive Hack) : r/3dsqrcodes

Ordinary Sonic ROM Hack (Genesis/Mega Drive Hack) : r/3dsqrcodes

Sally Acorn in Sonic X 2 : r/SallyAcorn

Sally Acorn in Sonic the Hedgehog 2 : r/SallyAcorn

Sonic 2 Long Version / Sonic 2 with Knuckles Long Version (GEN Hack by Sonic Hachelle-Bee/Esrael) : r/3dsqrcodes

Knuckles the Echidna in Sonic the Hedgehog (official build by Sega, existence unconfirmed), Lost Media Archive

Knuckles the Echidna in Sonic the Hedgehog Sega Genesis Game

Hack~ Knuckles the Echidna in Sonic the Hedgehog (Mega Drive) · RetroAchievements

Knuckles in Sonic The Hedgehog 2 (Sega Genesis Hack Gameplay) Part 1

Topic: Requests/Ideas - Knuckles the Echidna in Sonic the Hedgehog 2 · RetroAchievements

Sonic 2 SMTP (Mega Drive / Genesis Hack) - Gameplay (Knuckles and Tails)

Play Knuckles the Echidna in Sonic the Hedgehog (Sonic the Hedgehog Hack) - Online Rom