Secret Area in Monkey Dogfight
Go to Monkey Dogfight and set it to survival mode(so you'll have plenty of time). Choose the Space Monkey Wars level. Fly down until you reach the floor. Then fly into one of the ditches in the floor. Then while staying on the ground in the ditch fly straight through the wall. You should be in a big pitch black area outside of the arena. If you fly to low you'll hit a big pool of water.