Ice Queen is the gender-swapped version of the Ice King, created by the original series designer, Natasha Allegri. She has winter/ice-related powers like Ice King. She will be in "Adventure Time with Fionna and Cake". Ice Queen captures princes, while Ice King captures princesses.
Natasha Allegri has stated that the Ice Queen is far more cruel and evil than the Ice King. Supposedly this is to counteract the fact that she is also far more physically attractive than her male counterpart, aside to the fact that she is female, being physically attractive is the only difference between the two.
Fionna with The Fake Prince Gumball
The Fake Prince Gumball unbuttoning his shirt.
The Fake Prince Gumball revealing whats in his shirt.