Fantasy Drivers
To unlock the Fantasy Drivers enter the following name in the Create-A-Car option:

First Name: Extra
Last Name: Drivers

Then you should see a thunder plates for the Fantasy Drivers.

Race as Dale Earnhardt
To race as Dale Earnhardt you must enter his name in the Create-A-Car option (put Dale for a first name and Earnhardt for the last name). Once you enter his name you should get a Thunder Plate for unlocking Earnhardt.