Discovery Island is an ominous island explored in Mother 3.5. It is a rainy island covered in thick jungles. Basically, it's off-limits to people who aren't affiliated with the Pig Army. They say the reason for that is because "The discoveries made on this island are so wonderful that unless you're a Happiness Researcher, you'll faint from pure joy! That is why we ask that you please stay away, so that instead WE bring the discoveries of happiness to YOU." In truth, Discovery Island is the location of the Discovery Laboratory, a mysterious facility where experiments of various sorts are conducted to construct deadlier, more dangerous island creatures. The jungles are teeming with loose creatures, or some just sent out for field testing. Deep in the jungle lies the entrance to the Fourth Cave of the Future.