Donkey Kong Country Returns is the fourth game in the Donkey Kong Country series. It is the sequel to Donkey Kong Country 3: Dixie Kong’s Double Trouble!, and is the first Country-line game in over a decade. The game is a 2D platformer developed by Retro Studios for the Wii, and was announced at E3 2010. It uses many of the familiar elements from the original game and Donkey Kong and Diddy Kong are once again the main playable characters. – wikipedia
With that said, Wikicheats.com has provided us a cheat list for the game!
Cheat: Infinite DK Coins
Note: You need Diddy for this cheat. Look for the first checkpoint in World 2-2 (Sloppy Sands). Here you can find two squid cannons underneath a bridge. Hit JUMP and UP to bounce from the lower squid to the higher squid. Hit the squid and drop to the lower squid again. Keep bouncing between them for infinite DK Coins.
Hint: Low Battery Bonus
As you choose your save file, Cranky will give you 3 1-Ups if you have a low battery charge. He’ll give you 5 1-Ups for no reason occasionally as well.
Unlockable: World 9, The Golden Temple
In every level except for boss levels there are letters to collect that spell out K-O-N-G. Collect the KONG letters in every level in a World to unlock a bonus level. Beat the bonus level and you’ll get a Rare Orb. There are 8 Rare Orbs to collect, one in the bonus level of each World. Once you have them all, the path to World 9 via The Golden Temple will be unlocked.
Unlockable: Mirror Mode
Beat the Golden Temple (World 9) to unlock Mirror Mode. In this mode, every level is reversed and you move from right to left (BACKWARDS!!!). You have only one chance and you won’t be able to use inventory items or Diddy. Good luck with that.