To enter the following codes you must go to the Front Office option. Choose "Create a Player" option. From there, enter the following codes and then save the name. When you return to the Exhibition Mode and to the Vs. Screen, you will be able to select from the hidden teams and stadiums.

Teams
Loin Cloth - Tiburon
Orrs Heroes - EA Sports
Coaches - All Madden
Leaders - All Time
Pac Attack - All 1960s
Steelcurtain - All 1970s
Gold Rush - All 1980s
Aloha - NFC Pro Bowl
Luau - AFC Pro Bowl

Hidden Stadiums
Jetsons - Astrodome
Dawgpound - Cleveland
Snake - Oakland
Big Sombrero - Tampa Bay
Dandaman - Orange Bowl
Olddc - RFK
Sharksfin - Tiburon
Ghost Town. - Wild West