American Idol judge Katy Perry took a tumble on Sunday night while dressed as Ariel from The Little Mermaid in honor ... Keep Swinging' Perry's Ariel costume proved limiting from the start.

Altoona Area High School senior Jillian Pierannunzio portrays Ariel as junior Camille ... fees and materials for the costumes and sets for “The Little Mermaid” is nearly $20,000, Cossitor ...