Just had something happen on this game that left me in absolute stitches. If you want to try it for yourself here's what you do:
1) Go to free play
2) Go to any road course (do not choose an oval track. I chose Daytona sports car circuit if it helps)
3) Put the maximum drivatars to one
4) Set the difficulty to unbeatable
5) Set player buckets to two, and make sure that they are not scored independently
6) Set group one car class to X, set group two car division to Forza Specials
7) Choose a really powerful X class car (I chose the Renault R.S. '17)
8) Now load the track, and there should be one Ford Transit SSV along with your Renault R.S.
9) Make sure the starting type is set to Rolling
10) Start the race
11) Enjoy the hilarity that ensues
12) Try not to pass out
If nothing funny happens right away, try setting the group two division back to Any, and then switching it back to Forza Specials.