Olivia Olson is an American singer and actress. She voices Marceline 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."