Perfect Striker contains two additional, hidden teams. 
There are two ways that you can get these two new teams: 

1.Play through and beat the league mode.

[or]

2.Enter the following code (at the title screen): 

Up, L, Up, L, Down, L, Down, L, Left, R, Right, R, Left, R, Right, R, B, A,
and then hold down Z and press Start.

------------------------------------------------------------------------------

Big Head Players by N64 HQ
~~~~~~~~~~~~~~~~~~~~~~~~~~
To get "big headed" players in Perfect Striker, just enter the following code
at the title screen: Top C, Top C, Bottom C, Bottom C, Left C, Right C, Left C,
Right C, B, A, and then hold down Z and press Start. Look familiar? Yep, it's
the old Konami code.