He was voiced by Trey Parker by taking in helium to create the distinct high pitched voice. Nelson's only appearance is the episode " With Apologies to Jesse Jackson ", in which he first appears to give a talk at South Park Elementary to all students. Upon entering, he is almost immediately laughed at and mocked by Cartman, which Nelson dismisses believing he'll stop eventually.
South Park. Cartman and Dr. Nelson go toe to toe in a bare chested brawl where Cartman dominates. South Park S1 E9. Hankey finally comes to life to tell the people of South Park they focus too hard on what's wrong with Christmas and to remind them what the Holidays are really about.