Enter the options screen and choose the 
"Easter Eggs" selection. Then, enter
these codes: 

ALL BOBO - All Bobo teams 
ALL BOBO - Players have more endurancev 
BIG PIG - Large football 
FLEA CIRCUS - Tiny players 
Harder computer - Smarter cpu 
STROBE LIGHT - Frame by frame movement 
TWO D - Flat players