After the first one, he somehow got made into a new doll. Why any toy factory would take a burnt doll, and restore it, is beyond me. After the second one, his blood was still in the plastic at the factory...whatever. Then he shipped himself tp the military school, and got chopped up at the fair.
In Bride Of Chucky, he was put into the evidence closet, but his clothes were clean, which is impossible, after all the killing, and getting chopped up. In Seed Of Chucky, they made the film dolls that came to life, so whatever. In the last Chucky where he sent himself to his daughter, he not only had new and fresh clothes, but a new and fresh face over his sliced face, and fresh silky hair. So where did he get that new face, and the hair transplant? And how is he all fresh and new now?