Donkey Kong Country 2: Diddy's Kong Quest - 75 Kremlin coins

Beat Screech's Sprint without Racing:
Once you get half way through "Screech's Sprint" you will transform into the bird, and, normally, you will fly up to Screech and the race will start. If you come up right behind Screech to where the race will not start yet, and you fly upwards you must have both characters at this point for this to work, you will then hit the the ceiling and hurt yourself causeing yourself to blink. Quickly, while you are still blinking, pass Screech and head off to the rest of the level without having to worry about doing it in good time.

Cheat mode
When you get to the game select screen highlight two player contest and press down 5 times to get to music test and another 5 times to get to cheat mode. Once in cheat mode, press these buttons to activate the cheats:

Code - Effect:
Y, A, Select, A, Down, Left, A, Down - 50 Lives
B, A, Right, Right, A, Left, A, X - Hard Mode

Lost World:
To unlock the Lost World, you must pass the first world. In the all the other worlds, you will start to find a ''Klubba's Koisk'' in each world. When you visit one, a Kremling named Klubba will ask you to give him 15 Kremcoins to enter The Lost World. If you do give 15 Kremcoins to Klubba in a particular world, you will unlock one particular level of the Lost World.

"Animal Antics" Level - Give Klubba 15 Kremcoins in "K. Rool Keep"

"Black Ice Battle" Level - Give Klubba 15 Kremcoins in "Krem Quay"

"Fiery Furnace" Level - Give Klubba 15 Kremcoins in "Gloomy Gulch"

"Jungle Jinx" Level - Give Klubba 15 Kremcoins in "Crocodile Cauldron"

"Klobber Karnage" Level - Give Klubba 15 Kremcoins in "Krazy Kremland"

"Krocodile Kore" Boss - Beat the game and all 5 Lost World levels.

Sound Test:
Highlight Two Player contest and press Down, Down, Down, Down, Down