Donkey Kong Country 2: Diddy's Kong Quest · Super Nintendo (SNES) · 1995
Multiple hidden rooms and a secret world accessible through obscure warp barrels and out-of-bounds movement, including the completely optional Banana Bird Caverns containing collectibles unknown to most players.
Rare's Donkey Kong Country 2 contains an unusual density of hidden content: warp barrels concealed above visible level boundaries, bonus rooms requiring specific off-path movement to access, and the Lost World — an entire secret world requiring the player to find Kremkoins scattered across every level. The Banana Bird Caverns in Donkey Kong Country 3 extended this philosophy further, hiding collectible Banana Birds in cave areas behind the main map that could only be found by interacting with the environment in non-obvious ways. Rare's hidden-content philosophy in this era was unusually generous: the secret material was intended to give dedicated players hours of exploration that casual players might never encounter.
In the first level (Pirate Panic), look for a warp barrel above the level's opening section — jump from an elevated position to reach it and warp to a later world. For the Lost World, collect Kremkoins by completing bonus rooms in each level and spend them at Klubba's Kiosk to unlock individual Lost World stages.