To get 103%, first finish all the levels, (including Krematoa and its boss level, Knautilus), complete all the Swanky's Dashes and Cranky's Dojos, and collect all the bonus coins. You will have 100%. To get 101%, collect all the DK coins. Go to Funky and he will give you the Kong Copter. You now have 101%. For 102%, collect all the Banana Birds (20 in all). Make sure that you find all the secret caves, and complete all the minigames and Bear missions. For 103%, a completely beaten game, give all 20 banana birds to the Banana Queen (located near K's Kache in Pacifica). She will break free from her barrier and drop an egg on K. Rool's head. Dixie and Kiddy will pop out of the egg, and you will return to the main menu. When you see your file it will have 103%.
Alternate ending sequence
Defeat the last Boss in Krematoa and complete the game with all Bonus Coins, DK Coins, and Banana Birds.
Get all 98 Bonus Coins
Enter the Cheat aqua.
Kaos Kore: Secret cave
Follow the path up to the top of the waterfall. Swim to the two rocks and circle the two rocks in the shape of an eight to unlock a secret cave.
Music Player
Enter the Cheat music.
No Midpoint Barrels
Enter the Cheat harder.
Play Mini-games
Enter the Cheat Extras.
Reach Krematoa
To reach Krematoa (the Lost World), go to the four rocks east (left) of Mekanos. Stay on the rocks as you circle around it clockwise about four times and the volcano will replace the rocks.
Reach Pacifica
To reach the new exclusive to this game Oceanic based world, when you get the jetski use your turbo up the waterfall right where you started the game. Go up the waterfall after that and swim to the very hidden world marked by a K Rool Flag.