Halloween is a big deal at World 50. And while it says a lot about our culture, it also sheds light on how to build and reinforce culture in other organizations.

An important caveat right up front: While wearing costumes to work might sound like fun, this is about much more than making work fun, attractive to millennials, or creating Instagram-worthy posts. Do not get me wrong, we very much want World 50 to be a fun place to work—and I am proud of the fact that for many it is—but culture can be a real, tangible, competitive advantage when you get it right.

To put Halloween in context at World 50, we politely warn new colleagues who have joined since the last Halloween: “You do not want to show up without a costume!” Surely, many worry how seriously they should heed that warning (they probably should), what constitutes a legitimate enough of a costume (a head-to-toe rabbit suit is not overdoing it), and whether they might be better off taking the day off (no, it is too good to miss).

For Halloween 2017, nearly every World 50 associate showed up that morning in full costume. There were Star Wars characters: Alex wore a head-to-toe Chewbacca suit; Joan was Princess Leia; and Dan was Obi-Wan Kenobi. We had the Spice Girls. Not the singing group, but a play on the word with a group dressed as McCormick spice bottles. We had Mario and Luigi from the hit video game in full costume riding tricycles. We had Julia Child, Beyoncé (specifically her birth announcement), Game of Thrones characters, and everything you could imagine. Even those working remotely were in costume for the video meetings. Everyone voted on prizes for the scariest, funniest, best team, best overall and more.

In other words: We take Halloween very seriously. But buried in that is something more important: We do not take ourselves too seriously, and that is a big part of the World 50 culture. Without going into too much detail, in the business World 50 is in—building peer communities for C-level execs at Fortune 500 companies to help them stay ahead—it would be easy to get caught up in a sense of self-importance. But we need to remember our clients (“members” as we call them) join because of each other, not because of us—we even say, “It’s not about us.” To reinforce that, a core part of our culture is: “Take what we do seriously, but do not take ourselves too seriously.” But like any part of any culture, wanting or saying something has very little meaning or impact. It is what you “do” that matters. And therein is the learning for any organization.

Culture is not what you write on the walls or in an employee handbook. It is what people do. No amount of wishing for culture will get you there. Instead, consider developing a set of traditions—what I like to call rituals and artifacts—that build and reinforce the culture you want and need. Halloween at World 50 is one of the many rituals in every World 50 calendar year. The others—Hackathon, Internal Summit, Winship 5k, chili cook-off, everyone-gets-holiday-week-off goals, all-team meetings, Nicole Award, and more—are each unique but all serve the purpose of reinforcing culture. In the case of Halloween at World 50, we let our hair down, show some vulnerability, laugh at and with each other, and take lots of pictures—all physical manifestations and emotional expressions of not taking ourselves too seriously. The trophies we sometimes hand out and get displayed by winners in their work areas become artifacts that serve as “artifacts” to the traditions.

It is worth noting that by “culture” I am referring—in almost an anthropological sense—to how a community defines and (equally important) renews itself. In fact, “rituals” and “artifacts” are often what anthropologists talk about when describing a community or society, i.e., a unity of people with shared beliefs and norms. This is important because how to operate the business of World 50 could possibly be captured in a single three-ring binder that would be easy to photocopy. What would be nearly impossible to copy is a culture 12 years in the making that is very much aligned to delivering what we do. Since much of World 50’s success is based on nuance and having associates in nearly every role being able to say “this looks and feels like World 50” or not, no manual, process or set of instructions can duplicate that. Only culture can.

If having a culture that provides your business a sustainable competitive advantage is important to you, consider what traditions you maintain and seriously commit to rituals and artifacts that, year in and year out, build and reinforce it. Experiment and tweak. You will not get everything right the first try. But once you find what embodies the culture you want in actually doing, feeling, saying, etc., stick with it.