Cancer is often referred to in some of edd's videos.
"He" first appeared in Edd vs Cancer, and made a return in Eddsworld: Legacy when Thomas Ridgewell was summarizing Edd's history with cancer and his show.
Cancer is represented as a crudely drawn green dinosaur with a thick, v-shaped unibrow and two black dots for eyes.
In Edd vs Cancer, Cancer is carrying a microphone, before being punched in the face by a crudely drawn Edd.
In Edd vs Cancer, Thomas Ridgewell animated Edd beating up Cancer, who used on fist, and the screen suddenly fills with fire. Cancer itself, however, didn't disappear, signifying that Edd was still battling it.
In Eddsworld Legacy, Thomas Ridgewell summarizes Edd's life to those who didn't know about, including how he had developed leukemia in 2006, Edd's fight against Cancer, ultimately beating it into remission, the sudden return of it, and how it made his body give in.