At the create a player screen type the following names:
AT_MADDEN (_ is a space)-All Time Madden Team
SIXTIES-Team of the 60's
SEVENTIES-Team of the 70's
EIGHTIES-Team of the 80's
HOWLIE-AFC Pro Bowl '96-'97
SAN MATEO-A new stadium (The EA Stadium).
ELEC ARTS-Electronic Arts team (as good as Tiburon)
LEI-1996 NFC Pro Bowl Team
STATS MEN-Statistical Leaders Team
MAITLAND-Tiburon Spots Complex
When you are playing with two players in Madden 64, you can make a player fly. To do so, have the 1st player start pressing B to call audible as fast as they can. The 2nd player should press jump (left c) as fast as they can. The 2nd player will eventually jump continually on top of the screen. If you get him high enough, the instant replay will also be really screwed up.
To see the winning sequences at the end of the game. Turn your N64 on and hold the L, R, and the Z buttons when the EA logo comes up. You will now see some amazing endings. Also there is a hidden team. To unlock the team go to season mode and then to front office. Select create a player and then go to name. Enter "Tiburon" into the field and then go down to continue. Save it and then go back to the main menu, using the B button. Now go into exhibition mode and the team Tiburon will be selectable.