I found this picture, and it is the closest I could come to what my cake looks like. I like how they used cupcakes on the side of the cake. Cute touch for kiddies.
My recipe is pretty darn easy. Just make two 8 or 9 inch round chocolate cakes and let them cool. Meanwhile, mix pistachio pudding according to the pie directions on the box and chill in the fridge. Once the cakes are cooled, Put one cake on your serving dish and cut out a 4 inch round piece out of the middle of the cake. You can use this piece for a spider head if you want. Take your pudding and put that in the hole. Cover with chocolate frosting and then add the top cake. Frost like you would a normal cake and then decorate it however you want. I like twizzlers for legs, m&m's for eyes, etc. The cool part is when people cut into it, the pudding comes gushing out like the spider's guts. It is pretty awesome. You could do the same thing in cupcakes, just cut out the middle after they are cooled and then put the middle back in, frost, and decorate.