Well i know how to unlock these characters like.
Female cyborg. kill cyberden on Hard mode to unlock her.
Preistess: to unlock her just complete tomb to unock her.
Girl Zombie: beat mansion on hard mode to unlock her.
Robofish: complete the challenge tin man successfely to unlock robofish.
Frost alian: to unlock this character beat Planet (i cannot remember)but beat this level to unlock The Frost Alian.
Gingerbreadman: i am not sure about this one.
Swat man: beat chemical plant on hard mode to unlock this character.
Mr big: to get this character simply complete Chinese level on hard for this character.
Female Alien and Female stewedess: complete Spaceways on hard mode to unlock these 2 characters.

Hope this heleped submited by Simsmaster-2