 The effect of Kenny 's speech is achieved by Stone mumbling into his own hand as he provides Kenny 's lines , while the recorded audio is then edited with Pro Tools , and the pitch is altered to make the voice sound more like that of a fourth grader . As the technique of Kenny 's muzzled enunciation frequently implies , many of his lines are indeed profane and sexually explicit , the lengthier of which are mostly improvised by Stone . 
