Level 1 - You come across the Banana at the very end of the level before jumping down the hole, you can't miss it.
Level 2 - When you come to the part where you need to use the different Zartog heads to open the door and your going for the second Zartog head, but before climbing up the wall it will be directly across from the climbable wall on the other side of the water.
Level 3 - When you meet up with Luna the banana is to the right in the same room.
Level 4 - After you cross the river on two big lily pads its directly behind the three striped trees dead ahead.
Level 5 - When going for the two Zartog heads to open the door you must shoot a rock to make a platform to raise so you can cross, once its raised up go straight over the platform and behind some rocks to find the banana.
Level 6 - Just after lowering the bridge and when you get to the waterfall, there are little outcrops along the right wall with enemies on them, jump over and along them to find a banana on one of the outcrops.
Level 7 - During the side scrolling flying part you will come to the second group of butterflys that go straight up. When you reach the top go to the left and land on a platform with the banana on it.
Level 8 - No banana on this level.
Level 9 - You will come across a yellow Malgorain and he will ask you to take care of a monster for him. So after talking to him head around the back of the cliff and take out the big blue monster and all the little ones as well. Then go back and speak to him so he can give you a reward, the banana.
Level 10 - While making your way through the level you will come upon a pipe that breaks as soon as you step in, after its broken go directly to the left to find the banana on a platform.
Level 11 - At the very beginning you will fall through a trap door in the floor the banana is right there as soon as you land.
Final Boss - Directly in front of you, just on the ground between the silver statues.