As the boys start wandering through a tunnel, we cut to the space orb, which the moon people have dragged into a cave and are crawling over it and trying to open it like a giant puzzle box. Kate is scared by this and so grabs the elephant gun and tries to deter them by shooting it.
This noise alerts the boys, who start moving toward the orb through a fields of crystals and cave mushrooms, whence they are ambushed by a giant stop motion caterpillar.