S3E27 : A Phineas and Ferb Family Christmas

The boys decide to put on a traditional family Christmas special featuring their family, friends and a few very special guests, including Grammy winning recording artist Kelly Clarkson (playing herself). The episode features three new holiday songs - Isabella's "Let it Snow", a Buford and Baljeet rendition of "Good King Wenscelas" and the whole gang singing "We Wish You a Merry Christmas".