Rampage 2:Universal Tour
Cheat Option
Enter "BVGGY" as a password to unlock a "Cheats" selection on the options menu.
Credit Goes To: kidrOck via N64cc

Play As Noob Myukus
Enter "SRY3D" as password at password screen.

All Characters
To get all the characters in Rampage 2, put in the password N0T3T in the password screeen.
Credit Goes To: Julian Sham Ku via IGN 64
 Cheat Option
 Play As Noob Myukus
 All Charaters
 Play As Alien
 Play As Myukus
 Play As George
 Play As Ralph
 Play As Lizzy
Play As Alternate Alien
To play as the alternate alien with an unpronouncable name, enter the password: B1G4L
This should give you a purple form of Myukus that has all of his moves and favorite foods and also perfect stats.
Credit Goes To: Gokou via IGN 64

Play As Myukus
At the password screen type in N0T3T. In the code there is a zero and not the letter O.
Credit Goes To: Matt Waters via IGN 64

Play As George
To access George, enter the password SM14N.

Play As Ralph
To access Ralph, enter the password LVPVS.
Credit Goes To: Rob Waters via IGN 64

Play As Lizzy
To access Lizzy, enter the password S4VRS.
Credit Goes To: Talonsaurn via IGN 64