Olivia Olson was born and raised in Los Angeles, California, and lives with her mother, brother and father, Phineas and Ferb writer Martin Olson. She has appeared as a singer and actress on many television shows and has performed live in many Hollywood theaters, including The Comedy Central Stage, The HBO Theater and The Fake Gallery.
She is currently a semi-regular cast member of Disney's animated series Phineas and Ferb and supplies the voice of Vanessa, the sarcastic daughter of Dr. Doofenshmirtz. She also sings many of the songs in this Disney series, including a catchy duet called "Busted" with co-star, Ashley Tisdale. She also does the voice-over for the song "I'm Lindana and I Wanna Have Fun!" as Linda Flynn.
Still in her teens, she has written songs for Phineas and Ferb, is presently writing and recording her songs with renowned music producers Rick Nowels, Camara Kambon and Hollywood jazz great Rob Mullins, and for fun performs many of her original songs in YouTube videos.Olson has also appeared on The Tracy Morgan Show and was guest star on The Ellen DeGeneres Show singing with Ellen and actor Jack Black.
According to director Richard Curtis' commentary in the music section of the Love Actually DVD, Olivia's singing was so perfect, they were afraid the audience would not believe that a ten-year-old could really sing the way she did. They had to train her so that her singing would sound more believable.
Olivia also voices the character, Marceline the Vampire Queen in the cartoon, Adventure Time with Finn and Jake.