Carrie Underwood is known for her love of ball gowns but she kicked it with simple black leggings and a very special tee to team up with Miranda Lambert to raise awareness and support for kids with cancer. MORE: Miranda Lambert's love story with husband Brendan Loughlin is like something from a movie The country stars were among a group of singers who have joined the campaign for St. Jude Children's Research Hospital this holiday season. WATCH: Carrie Underwood's Christmas in Rockefeller Center