They Wasted A Perfectly Good Character / Fillmore!

• Brad Parnassus, the main villain of the pilot. He gets away with his crime and is clearly set up to be a recurring nemesis in the vein of rich businessmen or politicians from cop shows who use their connections to escape justice, but he never appears again after the first episode.
• Tehama and Anza have some interesting quirks and areas of competencies are the only other named security patrol members around besides Fillmore, Ingrid, O’Farrell, and Vallejo, yet have never played a significant role in an episode, it's a shame that we never learn more about them.
• The Bully Hunters from "A Dark Score Evened" and the way their actions bring up complicated issues regarding bullying and retaliation feels like it could have been brought up over multiple episodes, or at least had recurring characters involved.
• Francine Bishop from "The Shreds Fell Like Snowflakes" only gets one appearance despite being a compelling Young Entrepreneur with her ice sculptures and acting as the loyal and protective sister of Vallejo's disgraced old partner. Additionally, she attempts to get revenge on Vallejo for not standing up for her brother, using an impressively complex plan that she refuses to abandon even after her brother tells her to let the grudge go. Many fans would have loved seeing her continue that feud in future episodes and/or make peace with Vallejo, but neither ever happens.
• Robert Chestnut from “Links in a Chain of Honor”. He is the president of the Absurdly Powerful Student Council, an ex-safety patrol member, a secret Caring Gardener, and someone pressured to live up the legacy of his older brothers while also pressuring his younger brother (who he does have some affectionate moments with) the same way. He could have been a good semi-regular, but only appears in one episode as the culprit, with the series never even exploring the fallout of his actions and exposure.
• Antonia and Nicky Larkin from "Cry the Beloved Mascot" are a pair of prankster siblings from a rival school who are always trying to one-up each other, with Antonia also being an accomplished mascot thief who brags about the amount of strategy her craft takes. They had the potential to be interesting guest or recurring characters, but only appear briefly on one episode, where they aren't even treated as serious suspects for longer than a minute.
• The members of B.A.G.A.S.T. from "Two Wheels, Full Throttle, No Breaks" are a Vigilante Militia of skaters and wheelchair hockey players out to catch thieves that the safety patrol can't. It would have been interesting to see them as a regular presence, getting to show off their skills and sometimes helping, sometimes hindering the safety patrol while providing some in-depth commentary on vigilantism and its relationship with law enforcement. Instead, they are only in one episode, and neither their personality nor their skills get much showcasing.
• Randall, Augie, Tony, and Alistair are all characters who show up in the first four episodes of the show and have somehow been helped by Fillmore and Ingrid, (Although Augie was helped in the season two episode 'This Savior, A Snitch' and not his debut episode) how come the show never had them trying to repay either of them in future episodes? Considering the fact that season two was not meant to be the last season, it is arguably likely that they were meant to return, but the show got canned before they could do so. How awesome would it be if all of the people Fillmore and Ingrid helped ended up pulling a move similar to what the Safety Patrol did in 'Immune To All But Justice' and show up when Fillmore and Ingrid (And perhaps even the rest of the Safety Patrol this time) are fighting a losing battle, resulting in the tides being turned?
• Recurring cheerleader and school reporter Cheri Shotwell never has more than a minute or so of screentime per episode where she appears, not even in the episode where her crush Oscar is the culprit or the heroes investigate another cheerleader's disappearance. She also barely talks to Ingrid again after overenthusiastically welcoming her to school and is completely absent from some of the episodes where it would have made sense for her to appear, such as "Nappers Never Sleep" (which features some of her fellow cheerleaders in notable roles) and "The Nineteenth Hole is a Shallow Grave" (where her possible brother or cousin Cuzzy Shotwell has his golf match followed by other school reporters, is threatened into throwing a miniature golf tournament and is questioned by the safety patrol). In the latter episode, her either helping or hindering the investigation into Cuzzy could have also provided some commentary on how police and the media can either help or hinder each other.
• Fillmore's Evil Former Friends Sonny and Penny are both crafty foes who manipulate him but have some desire to reconnect with him. They could have been interesting recurring suspects but each only gets one episode.
• Mr. Delancey, the most colorful and unorthodox (but still reasonable) teacher in the show and his student Eric Orben, a Friend to All Living Things and Amateur Sleuth with a Jerkass Façade that has been taking a toll on his personal life, both have decent recurring character potential but take until the series finale to appear.