Bake and cool Cars cake. Ice cake sides, background areas, headlights, mouth, front windshield, side windows and blue lightning bolt smooth. Using tip 3, outline car details and number; pipe in eyes (smooth with finger dipped in cornstarch); add dot pupils and rivets on hood. Cover tires with tip 16 lines. Cover car, yellow lightning bolt and number with tip 16 stars. Add tip 3 outline muffler. Pipe tip 5 bead bottom border. Position cake on fondant-covered board.