how about in the egg quest game, an extreme dificulty that asks for credit shop eggs and seasonal eggs, would give lots of tu.

Or maybe something like the class change for the resident planet. But just once. Cannot be buyed in the credit shop like the extra class change. For not everyone to move to a certain planet, There will be a limit of residents to each planet, some new spaces wil appear ramdonly and this wont apply for new registering people.