The basic rectangular shape of Bart's head is described by director Mark Kirkland as a coffee can. Homer's head is also rectangular (with a dome on top), while spheres are used for Marge, Lisa, and Maggie. Different animators have different methods of drawing Bart. Former director Jeffrey Lynch starts off with a box, then adds the eyes, then the mouth, then the hair spikes, ear, and then the rest of the body. Matt Groening normally starts with the eyes, then the nose, and the rest of the outline of Bart's head. Many of the animators have trouble drawing Bart's spikes evenly; one trick they use is to draw one on the right, one on the left, one in the middle, then continue to add one in the middle of the blank space until there are nine. Originally, whenever Bart was to be drawn from an angle looking down so the top of his head was seen, Groening wanted there to be spikes along the outline of his head, and in the middle as well. Instead, Wes Archer and David Silverman drew him so that there was an outline of the spikes, then just a smooth patch in the middle because "it worked graphically." In "The Blue and the Gray", Bart (along with Lisa and Maggie) finally questions why his hair has no visible border to separate head from hair.