Knuckles in Sonic the Hedgehog is a title indicating additional content featuring Knuckles. The description is vague, so it is uncertain if this is a completely separate game or additional content/characters added to Sonic the Hedgehog on the Master System. It is also unclear whether this is an official release, fan-made content, or a ROM hack.

Knuckles in Sonic The Hedgehog

King's Quest - Quest for the Crown (USA)