International Superstar Soccer 64

Big Heads: At the title screen, press C-U, C-U, C-D, C-D, C-L, C-R, 
C-L, C-R, B, A, then hold Z and press Start.

Extra Teams: At the title screen, press Up, L, Up, L, Down, L, Down, L, 
Left, R, Right, R, Left, R, Right, R, B, A, then hold Z and press Start.