Crash Nitro Kart Cheats

As soon as you get 3 trophies, you can race Krunk. When you are racing
him, Krunk will drop spikes. If you hit one, jump as much as you can.
Then successfully beat him and you will get a key and a cutscene.

Accomplish the following tasks to unlock the corresponding FMV sequence at the "Extras" menu:
Team Bandicoot

Fake Crash:
50+(fifty or more) boosts with Team Cortex in Adventure Mode
Pura:
50+(fifty or more) boosts with Team Bandicoot in Adventure Mode

(not sure if it works - got it off a site thats not always reliable)

In Gameplay pause, then hold L1,L2,R1,R2 and while holding them press TRIANGLE CIRCLE CIRCLE TRIANGLE SQUARE CROSS

Dingodile - Beat Red Gem Cup
Fake Crash - Do 50 consecutive boosts on any track in adventure mode on the Evil team
N.Tropy - Defeat all N. Trophy ghosts in race time trial mode
Polar - Beat Blue Gem Cup
Pura - Do 50 consecutive boosts on any track in adventure mode on the Bandicoot team
Velo - Earn two sceptors in Adventure mode.One with each team.
Zam - Beat Purple Gem Cup
Zem - Beat Green Gem Cup

Complete the tasks listed to unlock the corresponding characters.
Dingodile: Win the Red Gem Cup.
Fake Crash: In Adventure Mode, do 50 consecutive boosts with the evil team.
N. Tropy: Beat all of the N. Tropy Ghosts in Time Trial Mode.
Polar: Win the Blue Gem Cup.
Pura: In Adventure Mode, do 50 consecutive boosts with the Bandicoot team.
Zam: Win the Purple Gem Cup.
Zem: Win the Green Gem Cup.