Olivia Olson (born May 21, 1992) is an American singer and actress. She is known for her role of Joanna, singing "All I Want For Christmas Is You", in the 2003 motion picture Love Actually. She is presently a cast member of Disney's animated series Phineas and Ferb and supplies the voice of Vanessa. She also sings many of the songs in this Disney series, including the duet "Busted!" with Ashley Tisdale.