Editing Fillmore! (section)

===Recurring===
* Mr. Collingwood (voiced by [[Kyle Gass]]) is one of the teachers 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, 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, he wound up being a witness to a set up on Filmore and is asked to testify at a student council meeting to clear Fillmore's name.
* Mrs. Cornwall (voiced by [[Holland Taylor]]) is the algebra teacher at X Middle School and a student in 1956. She strongly believes in the school's honor code. In "A Cold Day at X" she places the answer key to one of her tests out in the open to prove her belief in the 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 (actor)|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 dressed like a sea captain, which is appropriate, considering that he is a member of the Paddle Boat Club. 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 (actor)|Michael Welch]]) is another blonde X Middle School reporter.
* Wayne Ligget (voiced by Lukas Behnken) is Fillmore's original Safety Patrol partner before he eventually moved away and was replaced by Ingrid when she came to X. He is best friends with Fillmore, and before Ingrid became Filmore's partner, Filmore refused to have any partners because he was still greatly affected by Wayne's departure. He has light brown hair. As such, little is known about him and his background, but he is referenced a few times. However, he and Fillmore would meet up again in "South of Friendship, North of Honor", when the latter went to [[Tennessee]] where the former is  based and resides currently to take on a case there. Fillmore helps Wayne take down the schools 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, and as such, 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 [[Lobster fishing|lobstering]], in Sarah's case, being the latter. She was accused of damaging the "Lobsterman at Port" painting at an art museum in ''Masterstroke of Malevolence''