At the main menu, highlight either Quick Play or Arcade Play, no press and hold:
Right C and A together.
You should hear two swiching sounds if done correctly.
This will open up three new teams: Nintendo Plumbers, Left Field Lefties and Nintendo Gamers
4/17/2001
Clone Teams
This code will give you a team of clones of one single person. Enter a Team Select screen and push Top-C seven times. Now, do one of the following, depending on who you want your team to be composed of:
Kobe Bryant: Press Bottom-C three times. Ken Griffey Jr: Press Bottom-C four times. Random NBA Player: Press Bottom-C five times. Nintendo President Minoru Arakawa: Press Bottom-C 10 times. Nintendo Power's Armond Williams: Press Bottom-C 45 times.
There's also other character teams you can have, if you push Bottom-C any number of times between three and 45.
5/8/2002
Long necks and big heads
Press up-c and down-c at mode selection screen. It will tell you about the secret room. press these buttons for codes Big Heads: c-up x2,c-down,c-left,c-right Bonus teams:c-up (x2,c-down Long necks:c-up(x2),c-down,c-up,c-down small players:c-up,c-right,c-down
9/22/2002
Tiny Teams
At the Secret Room, press..... -Tiny Home Team: C-Up, C-down -Tiny Away Team: C-up, C-Right -Tiny Both teams: C-up, C-right, C-down