Play as Emperor Velo:
Get a 100% completion in Adventure Mode as Team Cortex.

Play as Fake Crash:
On a single track in Adventure mode playing as Team Cortex, get at least 50 boosts.

Play as N. Trophy:
Beat every N. Trophy ghost racer in Time Trial mode.

Play as Polar:
Win the Blue Gem Cup.

Play as Pura:
On a single track in Adventure Mode playing as Team Bandicoot, get at least 50 boosts.

Play as Real Velo:
Win two Scepters.

Play as Zam:
Win the Purple Gem Cup.

Play as Zem:
Win the Green Gem Cup.

Thanks to Revolution readers Kly Kly 89 and Nickydemus!