Olivia Rose Olson is an American singer and actress. She voices Marceline Abadeer in Adventure Time. She has also done voice acting on Phineas and Ferb as Vanessa Doofenshmirtz. Her adoptive father Martin Olson, who is also a screenwriter from Phineas And Ferb, voices Hunson Abadeer. She has posted videos of her singing on YouTube; her original songs include: "Sunny," "Loving You And Me," "Your Friend," "Sick 'n Tired," "Barriers," and "Suspicious."
Tom Kenny met Olivia when she was a baby because he was a comedy act at Martin Olson's club.
She also went on to voice Bliss from PowerPuff Girls.