"Pie Jesu" is a movement from Gabriel Fauré's Requiem. It can be heard in the Season Eleven episode "Lice Capades".
Background[]
As Clyde's head becomes less uninhabitable for lice, Travis is left to die after being shot by the Vice President Greg. Travis is then picked up by a fly, who transports him to a place where lice have lived for generations, never being disturbed. The camera zooms out and it is revealed that this place is Angelina Jolie's pubic hair and the lice here are crabs, hence their appearances being different from head lice.