Random team select:
Press Up + Turbo at the team selection screen.

Random player select:
Press Up + Turbo after selecting a random team.

Hidden stats:
Press Left + Extreme on the team select screen to toggle the stats display for each player.

Joke screen:
Hold Start and turn on the PlayStation to display a screen that resembles assembly and C code.

Big feet:
Hold Left or Right when exiting the Big Head selection screen.

Short players with big heads:
Press Up, Down, Left, Right, Down, then hold Up and select the "Yes" option on the big head selection screen.

Hidden mini-game:
In a four-player game, hold Up + Extreme on all four D-pads when exiting the select screen. A four-player game called Head-er-oids will begin.

Marshmallow treats:
Hold Up on all D-pads just before the screen dims at the end of the title sequence.

Hidden team select:
Press Down + Turbo to make the cursor and team choices disappear while they are being selected.