My Little Pony: The Movie will hit theatres next October and will feature an A-list voice cast, including Kristen Chenoweth, Liev Schreiber, Taye Diggs, Emily Blunt, Uzo Aduba, and more. Now, it has been announced that one more pony will join the paddock, as Sia will contribute two original songs to the soundtrack and play pony popster Songbird Serenade. And of course, the horse version is also wigged out.