First, I baked a carrot cake with a regular sheet cake pan. After it baked and cooled in the refrigerator, I cut out the shape of the car and piled up the scraps to make the big bumps above the wheels. I frosted it lightly with a knife, placed 4 chocolate covered Oreos in the wheel spots and put it back in the refrigerator to set.
After the frosting hardened a little, I piped more white frosting all over to give it a 3 dimensional look. The red frosting was then piped onto the sides for the circles and along the front to make the M pattern characteristic of Speed Racer. Store-bought sugar numbers and letters were placed on the cake to spell out Happy Birthday Isaac and the number 5 along the side. I used a plastic windshield from an old toy airplane as the windshield for the car. At the very end, I decorated the side with a few Hot Wheels cars.