By scanning select Ranger Key toys you can unlock additional Rangers for use in game. The only keys that unlock additional characters are the red ranger ones.

Ranger	How to unlock
Dino Thunder Red	Scan Dino Thunder Red Key.
In Space Red	Scan In Space Red Key.
Lost Galaxy Red	Scan Lost Galaxy Red Key.
Mighty Morphin Red	Scan Mighty Morphin Red or Armored Red Key.
Time Force Red	Scan Time Force Red Key.
Turbo Red	Scan Turbo Red Key.
Wild Force Red	Scan Wild Force Red Key.
Zeo Red	Scan Zeo Red Key.