Of all the characters on Abbott Elementary, there’s one who never fails to make me laugh. I’m talking about Mr. Johnson, the janitor whose dry humor and droll facial expressions make him one of the funniest personas on ABC’s hit comedy. Here’s what we know about Mr. Johnson: He’s probably in his 70s. He’s worked at Abbott forever, his institutional knowledge rivaling that of the longest-tenured teachers. He has alluded to past lives as an Olympic athlete, a nude model, a champion rib eater, and Dorothy Hamill’s paramour. He thinks that lizard people live under the Denver Airport and that the Illuminati run the world. He does not believe in the moon (not the moon landing—the actual moon). All of this is to say that Mr. Johnson’s origin story is mostly a patchwork of jokes: We don’t know anything substantial about the guy, not even his first name.

In a lesser comedy, he’d be a two-dimensional character who floats through the background, peppering in laughs as necessary. Not so with Abbott. Even without a fully fleshed-out past, Mr. Johnson has become a core part of the show, a character who seems to exist entirely in the present tense. He’s crucial enough that the actor who plays him, William Stanford Davis, was promoted to a series regular in Season 2. As the school’s janitor, Mr. Johnson is the gatekeeper to Abbott, bringing us in and contextualizing the everyday interactions within the school.

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In contemporary English, janitor refers to someone whose job it is to take care of a building, usually a hospital or a school. The job entails cleaning and keeping a place orderly by sweeping floors, wiping down counters, and taking out trash. But that’s not all janitors do. The word comes from the Latin janus, which means “arch” or “gate” and is also the name of the two-faced Roman god of doorways and portals. This etymology makes sense when you consider that people like Mr. Johnson are also ushers and space definers: They prepare a building before we even enter it, look after it while we are there, and continue to care for it after we’ve left. Part of their job is to pay attention—to the structures they oversee, yes, but also to people who pass through their doors.

Mr. Johnson encapsulates this role perfectly. He’s seemingly everywhere within Abbott’s walls, meaning he notices the emotional weather of the teachers and students inside. In Season 1, he’s among the first people to detect the romantic feelings between the teachers Janine and Gregory, raising his eyebrows at what looks like a lover’s quarrel. In Season 2, when the history teacher, Jacob (Chris Perfetti), has no idea why his students are obsessed with a show about talking socks, Mr. Johnson appears in the classroom doorway and begins speaking the program’s indecipherable language with bewildering fluency. He knows what the young people are up to just as much as he knows what the adults are thinking. Sometimes he’s the school’s protector: He also knows that if the scoreboard in the gym goes above a certain number, it’ll come crashing down. When the smooth-talking businessman Draemond fails to convince a gym-full of parents that Abbott should become a charter school, it is Mr. Johnson who sweeps him off the stage, physically enacting everyone’s disdain.

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It’s not just that Mr. Johnson sees everything; everyone sees Mr. Johnson too. In a late Season 2 episode, the teachers at Abbott vote on which of them should get two free tickets to an NBA game. The prize is supposed to go to an educator, as a paltry show of appreciation from the district. But the principal, Ava, announces Mr. Johnson as the unanimous winner, to his delight. When someone complains that he’s not a “real teacher,” he retorts, “You know how many classes I subbed?” He knows he deserves the tickets—he may not have the credentials, but viewers have seen him called to “teach” class after class, filling in the cracks of a broken (and broke) public-education system.

Ava asks the obvious question: Why did everyone vote for Mr. Johnson? One teacher, Melissa, responds that she chose him because she was annoyed with everyone else. But his landslide victory shows just how enmeshed he is in Abbott’s fabric. He’s the person every teacher thought of first, besides themselves, to put on the ballot. He is a vital part of the school, so much so that he’s almost synonymous with it. Abbott Elementary is a show that puts the hilarity, grossness, frustration, and joy of public schools on full display, so audiences can see how much energy and love goes into these institutions. They’re places where children learn, places of work, places where the community gathers to handle crises and hold celebrations. Wry, hardworking, and a little bit quirky, Mr. Johnson embodies the many-faceted world of Abbott in all its splendor and stumbles.