At the Cheat Menu, enter any of the following "Codes":

SCLLYMLDR = Alien Stadium
TRBMN = Infinite Turbo
RGBY = Rugby Mode
BTTRFNGRS = More Fumbles
HSPTL = More Injuries
BCHBLL = Big Football
FLBBR = Flubber Ball
HSNFR = Smoking Ball and Players
SHRTGYS = Small Players
TTHPCK = Thin Players
MRSHMLLW = Fat Players
PPCRNRTRNS = Landmines on Field
BGMNY = Large Coin at Toss
FRRSTGMP = Slow Motion