In Donkey Kong Country Returns for the Wii, there is a hidden World 9 you can unlock called The Banana Temple.
The first thing you need to do is collect all of the K O N G letters. Every level in a world (besides boss levels) contains hidden K O N G letters you can collect. If you collect all of these letter in every level in a world, you’ll unlock that worlds bonus level.
Once you beat each bonus level, you’ll receive a red orb for that bonus level. Collecting all eight red orbs will unlock the hidden World 9: The Banana Temple.