Collect the indicated number of components to unlock the corresponding upgrade for Stewie's ray gun.
When in the hospital level when playing as Stewie, there are hidden components. When you reach the rooms with the pregnant women, jump on their stomachs. First, a baby should fly out. If you jump on her again, nothing should come out. If you jump on her usually three or four times, a component for Stewie's ray gun will fly out onto the floor. Do this with every pregnant woman in the level, even the ones who shoot missiles out of their stomachs. Only one component is in each woman. After it comes out, there are no more.
On the Helen Keller level, do not move. If you touch her you will lose.
In Burtrums lair, at the part with the areas on the walls that have electric force field. When you hit the switch that removes the force field from the one that has the metal containers filled with deadly gas. Go down to it and destroy the containers and the camera will show a lot of the wrenches that give you 10 ray gun pieces each. The wrenches are right next to the switch to remove the force field.