Blockbuster Broadway smash
Wicked the Musical
is celebrating its 15th anniversary this fall with
A Very Wicked Halloween
, a televised concert on NBC featuring performances of the show's hit songs by various
. Not only will original cast members Idina Menzel and Kristen Chenoweth reunite for the special, but Ariana Grande will be on hand as well to celebrate her favorite musical. Today she revealed what song she'll perform and...we're shaking.