Bake and cool car, sheet cake and 6 cupcakes. Position car cake on board cut to width of cake and 1/2 in. longer at each end. Build up icing on front and back end of car to square off corners.
Ice windows and wheel areas smooth. Outline windows with tip 4. Trace lightning bolt pattern on both car doors with toothpick; outline with tip 4 and pipe in with tip 3. Overpipe wheel wells with tip 18 outlines. Cover car with tip 18 stars. Pipe tip 6 front grill and side panel lines; overpipe tip 2 lines on side panels. Attach 2 sugar wafers with icing to front of car for bumper; attach 2 smaller wafer pieces for bumper sides.
Cover front bumper with tip 2B lines, smooth if necessary with finger dipped in cornstarch. Pipe tip 10 outline bars and back bumper. Outline and pipe-in tip 4 front lights, back lights and back license plate. Pipe tip 3 lines on roof; add tip 8 outline luggage rack with tip 4 crossbars.
For roof lights, cover 2/3 of mini marshmallow with tip 4 in buttercream (pat smooth with finger dipped in cornstarch); leave one white end exposed to resemble light. Attach to car with icing. Print tip 4 name and pipe tip 4 decal on front grill.
Bevel ends of sheet cake by trimming sides to randomly measure 1 to 11/2 in. high. Cut cupcakes horizontally in half and attach randomly to cake top to create rugged terrain.
Generously ice cake with spatula; add brown sugar "gravel". Cut two hidden pillars to 4 in. high for back of car and cut two to 41/2 in. high for front of car; insert in cake. Position oval plate on hidden pillars to hold car. Cover pillars with icing, building up to blend with rugged terrain.
For car wheels, heat Chocolate Ready-To-Use Decorator Icing in microwave at 40% power for 20 to 30 seconds. Tint black; place 4 donuts on cooling grid over cookie sheet and cover with icing; reserve excess icing. Let dry on waxed paper-covered board. Pipe tip 3 outline treads with reserved icing.
Cut lollipop sticks to 3 in. lengths and insert into donut wheels to secure. Assemble cakes: Ice oval plate smooth; position car. Insert wheels on lollipop sticks under sides of car.
Note: Combine Red-Red and No-Taste Red for shade used.