Olivia is Mario's partner in Paper Mario: The Origami King. She plays a similar role to Kersti and Huey from past Paper Mario titles. She is King Olly's younger sister, and helps Mario foil his plan to fold the entire Mushroom Kingdom into origami. Her traits include her folded crown and hair, her yellow robe, and her spiky limbs. She can transform into large origami creatures called Vellumentals on certain Magic Circles. This can be done on the field or in battles.
She was folded to life by Olly on Mushroom Island, explored in the Great Sea.
Olivia behaves like a kind, naive and cheerful child. She is very friendly and can befriend anyone, like when she and Mario meet Bobby, Toads and even Bowser's minions. Olivia is also seen as sweet and innocent rather than demanding and sassy. She's very emotional and easily becomes amazed by many things. She also easily gets distracted from time to time when she sees something wonderful. Usually Olivia is really happy and sees the world in bright colors, but after Bobby's death she becomes heartbroken. From the beginning, Olivia believes that origami and flat paper can be friends and doesn't understand why her brother hates flat paper so much. She also believes to to the end that Olly can change and she initially didn't want to fight him. Olivia, despite being angry for what he had done, loves her brother and mourns after his death. She also always wanted to be an elevator operator in a fancy department store and is always open to share ideas.
- European website bio: "Olly's younger sister, Olivia uses her powers for good - teaming up with Mario to take down her older sibling. Olivia loves adventure, and will help you find the right path if you're ever stumped."
- In the Japanese version, Olivia tends to finish her sentences with "ですわ" (desu wa), a stereotypical speech pattern often used by princesses, noblewomen and arrogant women in Japanese media, similar to how Princess Peach talks in Itadaki Street DS and Fortune Street.