Big Head Mode(similar-At the title screen, just enter this code: 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. The announcer will say "Goal!" if you did it right. Go ahead and play the game, you're in for a big surprise.

Hidden Teams-Just when you though International Superstar Soccer 64 couldn't get any better a code comes along that unlocks six hidden teams in the game. Here's what you do to get hold of these babies. Using the control pad, input this code: 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.
The announcer will say: "What an incredible comeback!" if you did everything right. Just goto the team selection screen and you'll see a another group of teams, the All Stars. Have fun.