Heat oven to 350°F. Grease 12-inch pizza pan with shortening. Cut cookie dough into 1/4-inch-thick slices. With lightly floured fingers, press slices in bottom of pan to form crust.
Bake 18 to 22 minutes or until deep golden brown. Cool completely, about 20 minutes.
Spread baked crust with chocolate frosting to within 1/2 inch of edge. To decorate, sprinkle pizza with crushed granola bars to resemble sausage. Slice red gumdrops into thirds to resemble pepperoni. Cut green gumdrops into small pieces to resemble green bell peppers. Arrange gumdrop pieces on pizza.
Drizzle melted vanilla frosting over pizza to resemble mozzarella cheese. Cut into wedges or squares to serve.