Coat a 13 x 9 x 2-inch baking dish with nonstick cooking spray.
Line the bottom with a single layer of graham crackers. Cut pieces to fit if necessary. Save scraps. Cook butterscotch pudding following package directions, about 10 minutes. Pour over layer of graham crackers.
Place another layer of graham crackers over butterscotch pudding. Cook vanilla pudding following package directions, about 10 minutes, and pour over cracker layer.
Place a final layer of crackers over vanilla pudding. Cook chocolate pudding according to package directions, about 10 minutes. Pour evenly over the crackers.
Finely crush the remaining graham crackers and any scraps. Sprinkle over the top of the chocolate pudding layer. Refrigerate for 4 hours or overnight. Cut into squares.