Gill (Brilliant Boy): The most clever and resourceful boy in Baskerville, Gill is ever ready to tackle challenges and mysteries that baffle even the adults. Gill has a secret laboratory under his dog's house where he prepares the contraptions and concoctions he uses on his adventures. When it comes to battling monsters, Gill's weapon of choice is his trusty slingshot.

Bookman: After Gill, Bookman shares the distinction with Poetica as the top students at the Century Schoolhouse. Loyal and courageous, Bookman is the first to join his friend Gill on any adventure. As Brilliant Boy's sidekick, Bookman sometimes has to point out the obvious to his deep-thinking friend, especially when it comes to matters of romance.

Poetica: Quick-witted and sensible, Poetica is often the voice of reason on Brilliant Boy's more radical schemes. Poetica is the romantic interest of many boys at the Schoolhouse.

Stymie: Devious and self-serving, Stymie prefers to solve his problems using... more underhanded means. He often despises Brilliant Boy for being altogether  too clever. Stymie is cunning (in his own creative way) but he only applies himself for self-advancing purposes. Stymie is the leader of two young thugs: Brody and Kabel.