"Deck the Halls" is a song Mr. Hankey practices with the South Park Elementary students in the Season Twenty-Two episode, "The Problem with a Poo".
Background[]
The students practice this song as an orchestra for the Christmas Pageant with Mr. Hankey as the conductor. They play the song badly, to Mr. Hankey's frustration. Mr. Hankey wanted the Denver Symphony to perform the song but has to settle with the students due to budget cuts for the Christmas Pageant.
Only the instrumental version of the song is heard; no lyrics are sung.