There was a one time offer facebook added to all accounts when facebook credits was in its infancy. So any game you play, there will be an option somewhere in the game where you can get free credits/tokens/points by registering paypal details.

I used my offer on War Commander. If anyone still has the token offer, use it on War Commander instead. You get 50 facebook credits for free when you register paypal. You can then transfer that into tokens anyways.