Win a championship in career mode driving any of the three classes and you will unlock a few secret drivers...
Effect - Code
Don Garlits - Win a Season in Career Mode driving a Top Fuel Dragster
Don Prudomme - Win a Season in Career Mode driving a Top Fuel Funny Car
Jeg Coughlin Jr's 2004 Pro Stock Car - Win a Season in Career Mode driving a Pro Stock Car
Jim Dunn - Win a Season in Career Mode driving a Top Fuel Funny Car
Kenny Bernstein - Win a Season in Career Mode driving a Top Fuel Dragster