Virgil "Bull" Sharkowski is a bull shark who enjoys beating up smaller kids and stealing their lunches. However, his intimidating presence is offset by a high-pitched, squeaky voice that sometimes lessens the impact of his verbal threats. Despite being a bully, he also has a soft humane side that he doesn't usually realize he's revealing.
- Due to Bull being a water creature, he wears water-filled headphones over his gills to help him breathe; when he talks, he'll stop as his gills suck up the water with a loud noise.
- His nickname is a mildly obscure reference to the fact that bull sharks are known to be one of the most aggressive shark species.
- Bull has a big sister, Euripedes, who graduated CDMS prior to the beginning of the show and left a lasting impression in the school; a fact that has caused Bull to develop an inferiority complex at the mere mention of her name (despite the fact she is not only half Bull's size, but bullies via feminine taunts instead of physical abuse).
- In the online game, Chaos Tag, Bull has white eyebrows instead of his usual black ones.
- Bull also has a friend named EJ, but he is never shown in any of the episodes.
- Both Bull and Euripedes are voiced by Phil LaMarr.