Like in the SNES and GBA versions of DKC3, this game has a glitch with Koin. If he's far off-screen, the game considers him to not be present. Therefore, steel kegs can pass through Koin. This can make it easier to get DK Coins. Of course, after the steel keg passes through him, you'll want to run towards him so that the keg will hit him on the way back. It's useful if done correctly!