Unlock Atro Nut:
     Type in the following code at the code screen in the options menu
"ONESMALLSTEP"

Unlock Billyray Mudmullet:
     Type in the following code at the code screen in the options menu
"POSSUMPANCAKES"

Unlock Hottub Harvey:
     Type in the following code at the code screen in the options menu
"HARVEYSAYSRELAX"

Trick list:

Hart attack:                        Right, Down, Up
Mulisha air:                        Left, Down, Up
Gorrila Thumper:                    Right, Down, Left, Right
Back Flip:                          Left, Down, Right, Left
Cordova:                            Right, Down
Candy Bar:                          Up, Left
Airwalk:                            Right, Up
Blender:                            Up, Right, Left
Indian Air Superman Seat grab:      Right, Down, Left
Rollover:                           Left, Down, Left
360:                                Down, Right, Up
Heel Clicker:                       Left, Right
Bar Hop:                            Right, Left
Superman:                           Down, Up
Nothing:                            Up, Down
No Hander:                          Up
No Footer:                          Down
Saran wrap:                         Up, Right
Gorilla thumper:                    Right, Left, Down
Rodeo:                              Left, Up, Right
Backflip:                           Left, Down, Right
Front Fender Grab:                  Up, Up
Back fender grab:                   Down, Down 

Unlock The Astro Nut:
     Finish  the  entire  game with any bike rider. After you complete
that,  go to the main menu and select the freestyle games. Now look at
the  character  screen.  Under  the  very  last biker on the list, you
should have the new Astro Nut.

Unlock Sarcophagus Jones:
     Defeat  the  entire  field  of  racers in the 16 round supercross
series.  Upon  completion,  you  should  hear a dirt bike "revving up"
sound  effect  at  the  stats  screen.  Exit  and play a single player
exhibition  race,  and  when you select your biker, the new character,
Sarcophagus  Jones,  should be directly beneath the very last rider on
the list.

How to do a cookie:
     Press X while holding Triangle, then press Right or Left.

Tricks:
     Press Up, Down, Right for Helicopter
     Left, Down, Left, Left for Barrel Roll