All cameo FMV sequences:
Select "Features" at the main menu, then select "Create-a-Car". 
Enter "Seymore Cameos" as a case-sensitive name.

Dale Earnhardt:
To unlock Dale Earnhardt, win the Daytona 500 as Kevin Harvick (29 car). After 
winning the Daytona 500, a Thunder Plate will appear with Dale Earnhardt on it.
Alternately, go to Lighting challenge and play three of them. 

EA Sports Bio Bonuses 
If you only have Nascar Thunder 2004: 

Reach EA Bio level 16 to unlock the All-Star race at Lowe's 
Reach EA Bio level 18 to unlock the Bud Shootout at Daytona 

If you have Nascar Thunder 2004 AND Madden NFL 2004 saved games: 

Reach EA Bio level 10 to unlock the All-Star race 
Reach EA Bio level 12 to unlock the Bud Shootout

EA Bio bonuses:
Various other Thunder Plates can be unlocked by uploading your EA Bio from other 
2004 EA titles, such as NCAA Football 2004, March Madness 2004, Madden 2004, 
etc. 

Night tracks:
Go to season mode and then to "Custom Schedule". You can unlock night races for 
the day tracks.

Alternate night tracks:
Win the race that has a locked version of an alternate night track under the 
veteran difficulty, 3% race length, and damage on visual only. Repeat this method 
on all tracks that have a locked version of it.

Easy All Star race and Bud Shootout: 
Instead reaching the EA Bio levels for the All-Star race and the Shootout, just race 
a season under veteran at 3 or more % race length, damage on visual only, and 
brake and steering help, and win those races.

Driving locked cars:
In multi player mode, you can drive a locked car. This only works with one person 
at a time. Have a player choose their car, then have the other player go to the 
same car. It changes to a locked car. After that, they can choose their car.

Fantasy and night tracks and cars: 
Go to season mode. Choose custom for tracks. Then, choose locked tracks on 
medium. You can race at whichever locked track you choose. if you win race, you 
unlock a track. if you also have a locked car, you also win the first locked car.

Road courses:
To unlock a road course for Texas, Talladega, Pocono, Phoenix, Homestead or 
Daytona, race the original track on the medium or veteran difficulty. 3% is the 
easiest race length and the fastest.

Easy EA Bio increase:
An easy way to increase your Bio is to first end a career mode season. Then, save 
the season before selecting "New Season" at the top. After you have saved, go to 
the new season. As soon as you are done with re-rolling the stats (optional), the 
EA Bio bar will appear. Choose to save on that bar (only happens without 
autosave). Do not save the season, then exit. Return into your career and it 
should be back to where you can start the next season. Start the next season and 
repeat the process. After you have tried it a few times go into "My Nascar", 
select "Bio", and enter the recent history. In the recent history, it should show that 
you have finished two seasons in one day and the same car.

Alternate paint:
Win a race under the medium, hard or extreme difficulty setting to unlock a paint 
scheme for that driver. 

Exhibition and alternate event races:
Win a race under the medium, hard or extreme difficulty setting to unlock an 
exhibition or alternate race for that track. 

The Perfect Car:

Reach level 28 in your EA Sports Bio and you will unlock the pace car, Buster 
Auton. The pace car will not receive any damage when it is hit. 

Pace car:

Reach level 28 in your EA Sports Bio to unlock the Buster Auton pace car. Note: 
This car is damage-proof.