At the 'Driver DNA Lab' option highlight 'Celebrity Face Off' and beat the character on ALL 3 of their races to unlock the corresponding car.

Unock Audi 1.8T Quattro:
Beat Caballero in ALL 3 of his race challenges.

Unock Nissan Skyline R32 GTS-t Type M:
Beat Tarzan Yamada in ALL 3 of his race challenges.

Unock Dodge Viper SRT-10:
Beat Samuel Hubinette in ALL 3 of his race challenges.

Unock Ford Mustang Fastback:
Beat Djibril Cisse in ALL 3 of his race challenges.

Unock Nissan Silvia S15 Spec-R:
Beat Phil Morrison in ALL 3 of his race challenges.

Unock Toyota Corolla GT-S:
Beat Beau Yates in ALL 3 of his race challenges.

Unock Ford Mustang GT '05:
Beat Smudo in ALL 3 of his race challenges.

To get the following customised DNA lab cars you must first enter the code at the 'password' prompt to unlock a 'Special challenge' and then you must beat it to get the car.

Unlock Special Challenge #1:
Enter the code YTHZ

Unlock Special Challenge #2:
Enter the code GVDL

Unlock Special Challenge #3:
Enter the code RBSG

Unlock Special Challenge #4:
Enter the code BSLU

Unlock Special Challenge #5:
Enter the code MRHC

Unlock Special Challenge #6:
Enter the code MNCH

Unlock Special Challenge #7:
Enter the code KDTR

Unlock Special Challenge #8:
Enter the code DOPX

Unlock Special Challenge #9:
Enter the code PRGN

Unlock Special Challenge #10:
Enter the code JRWS

Unlock Special Challenge #11:
Enter the code WIKF

Unlock Special Challenge #12:
Enter the code FAMQ

Unlock Last Man Standing Challenge:
Enter the code KNOX


Unlockable Cars

Unlock Audi TT 1.8 Quattro:
Complete Special Challenge #1

Unlock BMW Z4 Roadster:
Complete Special Challenge #2

Unlock Holden Monaro:
Complete Special Challenge #3

Unlock Hyundai Coupe 2.7 V6:
Complete Special Challenge #4

Unlock Infinity G35:
Complete Special Challenge #5

Unlock Infinity Red G35:
Complete Special Challenge #6

Unlock Koenigsegg CCX:
Complete Special Challenge #7

Unlock Mitsubishi Prototype X:
Complete Special Challenge #8

Unlock Nissan 350Z:
Complete Special Challenge #9

Unlock Nissan Skyline R34:
Complete Special Challenge #10

Unlock Saleen S7:
Complete Special Challenge #11

Unlock Seat Leon Cupra R:
Complete Special Challenge #12

Unlock Ascari KZ1:
Complete Last Man Standing Challenge