Bulk Star:
Beat Celestial Valley in time attack mode under 3:20:00.
Formal Star:
Beat Frozen Hillside in time attack mode under 3:14:00.
Galax:
Complete 100 laps on any level to unlock him in Air Ride.
King Dedede:
Beast King Dedede in Event Stage 24 to unlock him in City Trial, or beat 1000 opponents to unlock him in Air Ride.
Meta-Knight:
Break 1000 boxes in City Trial to unlock him there, or get 30 minutes of total air time air time to unlock him in Air Ride.
Rex Wheelie:
Beat 100 enemies on Exhaled Stars in Air Ride.
Rocket Star:
Complete one lap on Machine Passage under 1:05:00.
Shadow Star:
Knock out 100 enemies with a quick spin.
Slick Star:
Complete two laps on Checkered Nights under 3:05:00.
Wheelie Bike:
Play all the standard courses.
Wing Star:
Cross the finish line in first place while in the air.
Extra movie:
Glide for one hour, total.