From Homestar Runner Wiki
In the Strong Bad Email animal, Strong Bad settles on Sterrance as what he would "like as" (look like) if he were his own made-up animal. He decides this after a lengthy series of other failures (documented in Made-Up Strong Bad Animals). Sterrance has a pudgy blue body with the crest from Strong Bad's Mexican wrestling mask and tiny boxing gloves for hands and feet. He also has wings, buck teeth, large nostrils, and a dangling yellow tongue.
Strong Bad thinks that Sterrance is way cuter than his "stupid, ugly, old, washed-up" The Cheat, and this insult starts a brief argument between the two characters.