On every level (not room), there will be at least one switch to unlock a new part of the area. You will know if you did not get a switch in that room if the door is red with a yellow star. Most of the levels guard their switches with things that can only be destroyed with the "Hammer" ability. You can only see The boss with the brown bullets once; there are other ways to get Hammer. Very few levels have Bonkers the Monkey (the Boss that is a monkey with a hammer), and he can give you the needed ability. First, complete every level and do not pay attention to the switch at that level if one exists. When you defeat the Nightmare Wizard, there will be a story about how King Dedede did not want to harm anybody. Then, go back to level 7-2. There will be a black rectangle with white lines in the middle at the top. You will go straight to Bonkers, but he will be stronger. Defeat Bonkers and suck him up. Go back to the levels you did not get switches on. Note: You may have to go to Bonkers more than once.