What are the 8 rare orbs?

The eight rare orbs are at the end of each of the eight Kong temples found in each world throughout the island. You get them after finishing each temple level. To unlock these temples, you must first get the K,O,N,G letters in every other level of that particular world to unlock that certain temple. For example, to unlock the temple in World 5, I must get all the letters in all the levels of World 5 in order to do so. These levels take a effort to unlock them for a reason, because they are very rare and challenging.

The levels (except for the World 4 temple) make the regular levels in that world look and feel like a walk in the park - it's that difficult to beat. Unlike the regular levels, these levels have no checkpoints but fortunately have no KONG letters for you to collect. The puzzle pieces are also very obvious and easy to get as well. Once you manage to get all 8 orbs and beat the game by beating Tiki Tong, you will watch a short cutscene in which four hidden monkey statues pop out and make a golden palace on the island.

Visiting the golden palace allows you to get to a golden banana mentioned by Cranky Kong throughout the game. Not only do DK and his buddy enjoy it, but it also literally warps them to above the sky. This bonus "world" is just one level taking place in the sky, full of fruits, platforms, and new enemies. Just like the other temple levels, there are no KONG letters and checkpoints, but the puzzle pieces are easy to get and there is not time attack mode unlike the other levels in the game.

Completing this level allows you to unlock Flip Mode, similiar to Master Quest or Hero's Mode in Zelda. Everything in the game is backwards and looks as if you are looking in a mirror while playing this game. Also, you only have one heart instead of two. Diddy Kong is nowhere to be seen and Cranky Kong's shop is absolutely off-limits. And if you manage to beat this mode, then you deserve a goldmedal and should be called a God from then on for acheiving the impossible.