Banana 1/blueprint: The other cave has Diddy's casplat. Defeat him and you are done.
Banana 2: The second one needs you to pound Diddy's switch. It sounds simple, but the banana is next to Funky's armory and you only have 50 seconds to grab it. Use the banana warps to your advantage and grab it.
Banana 3: This involves Diddy's Weapon the peanut popguns, and Cranky's move. Shoot the peanut switch and make your way up the appearing walkway. Go through the gap in the mountain to reveal a mineshaft. In the mineshaft, there's a tunnel. Going through this will lead to a gate. Chimpy charge at the piece of loose fencing and defeat the clomp. There will be a lowered button which when charged into will have a shaft appear. Pound the switch, defeat the clomps, and walk into the shaft. After this, there will be a minecart mini-game, complete that and the banana is yours.
Banana 4: In the shaft there will be a bunch of crates. Jump on those and there will be a peanut switch. Shoot that and a walkway will appear for 30 seconds. Go across and pound the switch to make the banana appear. After getting banana 3, go to the top of the mountain to grab it.
Banana 5: In the entrance cave there are 2 peanut switches. Shoot them to reveal a new area. Grab the banana and Diddy's done.