Every character is named after a street in
San Francisco, California.
Main • Cornelius C. Fillmore (voiced by
Orlando Brown) is a seventh grader at X Middle School and the main
protagonist of the series. He is a member of the Safety Patrol. Fillmore was previously a juvenile delinquent until Wayne Liggit recruited him into the Safety Patrol as an alternate to spending the rest of middle school in detention. Fillmore is known for going above and beyond the standards of other Safety Patrol officers. He almost never loses a target even if it means destroying school property. • Ingrid Third (voiced by
Tara Strong) is Fillmore's
goth best friend and partner on the X Middle School Safety Patrol. Before her arrival at X Middle School, Ingrid was a delinquent and was sent to a
reform school in
Nepal for an incident involving a
stinkbomb and a
piñata. Ingrid partners with Fillmore after he helped her clear her name. • Horatio Vallejo (voiced by
Horatio Sanz) is the junior commissioner of the Safety Patrol and Fillmore's immediate superior. Vallejo is often put at odds against Fillmore, such as when he is forced to take Fillmore off a case even though he does not want to, or Fillmore is close to solving it. He also often rebukes Fillmore for his reckless destruction of school property. • Karen Tehama (voiced by
Lauren Tom) is the crime scene investigator on the Safety Patrol who has a keen interest in
forensics and can usually be counted on to know the word on the street. • Joseph Anza (voiced by
Danny Tamberelli) is the partner of Karen Tehama, known for his bodyguarding training and like Tehama, tends to know the word on the street. • Danny O'Farrell (voiced by
Kyle Sullivan) is the crime scene photographer for the Safety Patrol, though it is often joked that he should not be qualified to be a Safety Patroller by Vallejo. He has a tendency to get on other people's nerves and has some deep thoughts, overreacting, and weird ideas. • Dawn S. Folsom (voiced by
Wendie Malick) is the principal of X Middle School. Folsom often threatens to turn the Safety Patrol office into something else if they are unable to solve the case. However, she does much for her students and staff, sometimes anonymously. • Vice Principal Raycliff (voiced by
Jeff Probst) is the school's vice principal and Folsom's right-hand man. Though he acts like a secretary or as a vice mayor in crime shows, he never really says much, but can be counted on to gush out school facts, figures and catchy metaphors at the drop of a hat.
Recurring • Mr. Collingwood (voiced by
Kyle Gass) is a teacher at X Middle School. • Augie Sansome (voiced by
Frankie Muniz in "Test of the Tested", Kiel Holmes in "This Savior, a Snitch"): In the former episode, he was suspected by Fillmore and Ingrid of stealing the answer sheets to the S.A.T.T.Y. 9 test, but what he really stole turned out to be packets of tartar sauce. In the latter episode, he becomes a witness to a set up on Filmore and testifies at a student council meeting to clear Fillmore's name. • Mrs. Cornwall (voiced by
Holland Taylor) is an algebra teacher at X Middle School and a student in 1956. She strongly believes in the school's honor code. • Librarian Lendrum (voiced by
Brian George) is X Middle School's librarian. • Cheri Shotwell (voiced by
Debi Derryberry) is the lively, bubbly, blonde-haired cheerleader who also serves as a reporter or interviewer. She also frequently hosts parties and sleepovers. • Philsky (voiced by
Michael Welch) is the school's reporter, who usually co-anchors with Cheri. • Vern Natoma (voiced by
Marcus Toji): Editor-in-chief of the school's newspaper. • Professor Third (voiced by
Anthony Head): College professor and the father of Ingrid and Ariella. • Jamie Townsend (voiced by
Chris Marquette) is a smart student who wears glasses. • Proper Kid (voiced by
Shaun Fleming) is a blonde-haired boy who is a member of the Paddle Boat Club and dresses as a sea captain. He is so called due to his always pointing out what is fit. • Lab Coat Kid #1 (voiced by
Chris Marquette): As his title suggests, he is one of the kids who wear lab coats and often involved in the lab or science class. • Wade (voiced by
Michael Welch) is another blonde X Middle School reporter. • Wayne Ligget (voiced by Lukas Behnken) was Fillmore's original Safety Patrol partner before he eventually moved away and was replaced by Ingrid when she came to X. Wayne and Fillmore reunite in the episode "South of Friendship, North of Honor", where Fillmore helps Wayne take down the school's distorted patrol sheriff and Wayne is subsequently named as his school's new safety patrol sheriff. • Frankie Polk (voiced by Lukas Behnken) is a blonde-haired boy who has an affinity for sketching and painting. He is president of the Art Club. • Sarah Beel (voiced by
Mae Whitman) is one of several students at X Middle School who either bear malice to the school mascot, Lobstee the Lobster, or to anything else associated with
lobstering. ==Production==