Olivia Olson

Olivia Rose Olson (born May 21, 1992) is an American actress, voice actress and singer-songwriter. She is best known for her voice role as Marceline the Vampire Queen in "Adventure Time." She also played the character of Joanna in the 2003 movie "Love Actually" and its 2017 short sequel "Red Nose Day Actually".
Her father is comedy writer Martin Olson.