Tony Hawk's Underground 2 Cheats

Type in 4wheeler for paulie
Type in sellout for that beverhuasen guy
Type in oldskool for the guy that teaches you the natas spin
Type in straightedge for perfect rail
I hope these come in handy for you

Go to the cheat menu and type it in

To unlock the R/V halfpipe and that mission for your character, play as Jesse James and jump over three cars.

The Star Wars Kid makes a second appearance in the final Classic level, Triangle. Grind the helicopter missiles in order to bust open two holes in the side of the mountain. There are three sets of windows showing aliens doing a variety of things including watching the Star Wars Kid demonstrate his ridiculous dance.

To unlock the R/V Half pipe, and that mission for your character, all
you have to do is be jesse james (the dude with that sick sick scooter)
and jump over 3 cars.

When you reach the Australia level, go to the fountain. You will find a headless statue near a crane carrying a koala head. This is Kenny the Koala, who was the mascot for the zoo level in Tony Hawk's Pro Skater 4.