I found a semi-secret area in Oleander's braining. AT the part right after you slide down the ladder with the fire cannons (about 1/3 of the way through the level) and you see Bobby Zilch, you drop down off a platform onto the ground.
Now, if you continue you jump on the floating platforms that are going in circles. But back near where you drop down there's a sign that says something like "restricted area" and if you go over there you drop down into a cavern with like ten figments. And then when you exit you're further ahead in the level.