Parker and Stone said a number of Cartman's characteristics which have endured throughout the "South Park" series started in "Damien". Specifically, his voice took on a higher-pitch that was more nasally and whiney than in previous episodes; Stone described it as a "self-indulgent accent". Some of his regular vocal mannerisms were also developed in the episode, including his use of the sound "Nyah" while saying the word "Here", and the way he says "Hey you guuuuuuys" while talking to his friends. Parker, who provides the voice of Cartman, said the characteristics came about naturally while filming the episode: "This show for some reason, for whatever reason, maybe I just lost interest, but I was trying all these messed up things with him and all these things sort of stuck."