The Magic Spheres are objects that are found in certain levels in Rayman 2: The Great Escape and in Rayman 3 (GBA). They are magical orbs that can be carried around like plums and kegs, and come in either blue or yellow (or perhaps gold and silver). They need to be thrown onto triangular pedestals of the same colour in order for something to happen, mainly for an important door to open to progress through the game.
Incidentally, the Blue and Yellow Pyramids the Spheres must be placed on are of the same shape, colour and luminosity as Axel and Foutch's heads. The manner in which Rayman must throw the Spheres onto the Pyramids in order to progress is also similar to the way he must knock the stalactites onto Axel and Foutch's heads in order to defeat them.
In Rayman Revolution, a third type of Magic Pyramid is encountered. These Pyramids are a pale blue colour, and are only found in one room (the room in which Rayman fights Boss Chenille). Rayman uses the Rain Mask to summon a raincloud over one; this causes a beam of light to shoot out of it into another Pyramid. When Rayman hits this one with his shot, it shoots a beam of light into another Pyramid. Rayman continues to shoot the Pyramids in this fashion until all of them are connected by beams of light. This causes Boss Chenille to appear. As Revolution, the only version of Rayman 2 in which the third type of Pyramid appears, is also the only version in which Grolem 13 appears, it is possible that they are connected in the same way that Axel and Foutch are connected to the first two types of Pyramid. Grolem 13's colour also matches that of the third type of Pyramid.