 He is sexually aroused by physical pain and injury, especially in regards to female patients of his, as shown in "Numb" when he displays a sexual interest in Bloberta Puppington when she injures herself by using a jackhammer as a dildo.After she heals and gets rid of the jackhammer, however, he loses all interest and refuses to even look at her.This fetish is likely his reason for becoming a doctor, despite his ineptitude.