Ski On Your Head
Go to Olympic mode and select Freestyle Aerials. Then pick any trick. As you go down the hill don't press any button. Wait until you have left the ramp then rapidly tap B. When you land your skier will jump forward and land on his head.
At the Options screen highlight Fighting hold L and press CRight CLeft CLeft CRight CDown CUp CUp CDown CLeft CRight CRight CLeft CRight CLeft.
Multiplayer Practice Mode
At the Title screen hold A on Controllers Two Three and/or four and use Controller One to highlight Practice and press A.
At the Main Menu hold B and press Start.
When playing against the CPU and not in Olympic Mode highlight the desired opponent and press CRight CRight CRight.
Pause gameplay and at the Options screen hold L and press CLeft CLeft CLeft CLeft CLeft CLeft CLeft CLeft CLeft.
Change Player Appearance
At the Options screen press:
CDown R head size alters bits 1 and 2
CLeft R body size alters bits 3 and 4
CUp R announcer's voice alters bits 5 and 6
100000 Stocky Players
010000 Stocky Players Big Heads
110000 Stocky Players Small Heads
001000 Small Players Small Announcer
000100 Large Players Large Announcer
000010 Crunched Players Small Announcer
000001 Elongated Players Large Announcer
110110 Large Players Small Heads Large Announcer
010010 Crunched Players Large Heads Small Announcer
010101 Large Players Large Heads Large Announcer
010001 Elongated Players Large Heads Large Announcer