Betty Grof

Betty Grof is a human woman revealed to have once been the fiancée of a man named Simon Petrikov, who would much later become Ice King. She and Petrikov had a very committed relationship until Petrikov obtained an enchanted crown, which gradually began to alter his mind and body. When Petrikov put on the crown for the first time, something he did terrified Betty and caused her to leave. Simon never saw her again, and he records on video his desperate wish to regain his sanity so that she might one day return to him.

In "Betty," Simon, who had been changed back to normal, was able to create a portal that linked to the past before he drove Betty away. He took this moment as an attempt to apologize to Betty, but instead she leaped through the portal to be with him, only later to find out that he was dying. The cause was the being Bella Noche, who withheld all the power from the wizards of Ooo. When Simon opened the portal, it was revealed the reason she left him was because she fled when he became crazed and was attacking her with his ice powers, and then because she went forward through the time portal, explaining why Simon never saw her again in the past. She took it upon herself to get Simon's powers back and also stated that she was going to try and find a way to keep him alive and free from the crown's curse. Arriving at the castle, Betty defeated Bella Noche and restored the powers to the wizards as well as the dying Simon.

She is later seen observing Simon, now the Ice King once again, in his castle. She exits on a flying carpet.

Personality
Betty doesn't make an actual appearance in the series until the episode named after her. In the episode, she is shown to be very loving and devoted to Simon. She is surprisingly bold and daring, as she went to face off against the creature Bella Noche by herself in an attempt to keep Simon from dying.

Like Simon, she appears to be quite educated in magical artifacts and was confident she could return Simon to normal.

Appearance
Betty is an adult woman appearing to have pinkish skin and auburn hair. In a picture on Simon Petrikov's wall, Betty is seen wearing glasses and a green turtle neck. In another picture, Betty is wearing a lab coat. This might suggest that she was in a field of study, such as science or medicine.

Trivia

 * Simon referred to Betty as his princess while he still possessed some of his sanity.
 * Adam Muto stated that the figure in the picture with Simon and Betty is "some sort of cryptid." A cryptid is a creature that has been sighted before but whose existence is unconfirmed by science.
 * Pendleton Ward and Rebecca Sugar have stated specifically that Betty and Doctor Princess are not the same person.
 * Betty's last name is an homage to Stanislav Grof, a psychiatrist who's one of the founders of the field of transpersonal psychology.
 * She is now the second human inhabitant of Ooo, meaning Finn is no longer the only human in that world.