Drive the Porsche
At the Car Select menu highlight car F hold L R Y and press Right. Car G will appear.
Drive the Truck
At the Car Select menu highlight car G Porsche hold L R Y and press Right.
Secret Rooftop Track
Enter the mode select screen highlight each option and press B. The screen will display each mode and flash to confirm correct code entry. Choose the "Time Trial" option. Highlight any track on the course selection menu hold X and press A. A rooftop track will appear with the background from the track that was originally highlighted. Press Y during the race for an overhead view.
Press Z during the replay to pause the sequence.