In the first week of September, red balloons began mysteriously appearing in a small Pennsylvania town.

Days later, the horror movie It smashed expectations and records with a $123 million opening weekend haul.

In between is the most unlikely of marketing campaigns – transforming a harmless item into the scariest symbol and promo product in America.

But first, let’s walk it back.

Popular author Stephen King released It in 1986. The novel would go on to become the best-selling book of the year. A TV miniseries adaption was released four years later, earning unofficial cult classic status and positioning the terrifying antagonist – Pennywise – as one of the enduring monsters of the modern horror genre.

Playing on the movie It, a “local prankster” placed red balloons all over the town of Lititz, PA. It went viral after the borough’s police said they were “terrified” (not really) in a Facebook post.

Who is Pennywise? It’s really a shape-shifting entity that haunts the small town of Derry, ME, taking the form of whatever it pleases to frighten its victims. Its most typical appearance is that of Pennywise the clown – a deeply unsettling fiend who uses a single item to attract children his way: a red balloon.

Anticipation for the new It movie was already high. Given its history, the movie is expertly positioned at the crossroads of two nostalgic phenomena: renewed interest in 80s-esque coming-of-age stories (thanks to Netflix’s series Stranger Things) and the surging celebration of early ’90s pop culture by millennials.

But of course, every movie needs a little bit (OK, a lot) of marketing. Among the ways that Warner Bros. promoted the movie was a guerilla marketing campaign in Sydney, Australia, tying red balloons to sewer grates and spray painting a message: "IT IS CLOSER THAN YOU THINK. #ITMOVIE IN CINEMAS SEPTEMBER 7".

Then the promotion took on a life of its own.

It happened in Lititz, PA – the 2013 winner of Coolest Small Town in America. Still, many of its 9,000-plus residents were not down with the red balloons that cryptically appeared. Tied to sewer grates and devoid of any message, the number of balloons totaled over 20, said local police. Was it the work of a prankster? A team of marketers? A killer clown living in the sewers? A massive Nena fan?

The Lititz Borough Police Department addressed the matter on Facebook, announcing that “a local prankster took it upon themselves to promote the movie” and then cheekily adding, “we give points for creativity, however we want the local prankster to know that we were completely terrified as we removed these balloons from the grates and we respectfully request they do not do that again.”

Soon enough, the “prankster” revealed its identity: a group of teenage girls who lived in the town. Self-professed ringleader Peyton Reiff copped to it on Twitter with photos and a message: “We tried to trick our friends but ended up scaring America! #redballoonlititz"

A group of teenage girls revealed themselves to be the red balloon culprits – and spend a good-natured 30 minutes in jail for their actions.

"It was like our big summer blowout," Reiff told PennLive.com, adding that the girls initially put the balloons where only their friends would see them, but then decided to also place them throughout the town. "We just expected it to be a small little thing." In a Facebook Live video interview with PennLive, Reiff noted that she took inspiration from the movie’s trailer and also the balloon promotion that occurred in Australia. “I was like, we should bring this to America,” she said.

In the end, the girls were brought to justice … with a 30-minute stay in the Lititz pokey, and plenty of red balloons to keep them company.

Lititz wasn’t the only place that wayward red balloons were spotted. Sightings were reported in Cloquet, MN; Girard, OH; Winston-Salem, NC and more. (One clever citizen placed a Pennywise cutout in a sewer grate in Tuscon, AZ.) Even so, nothing went viral like the occurrences in Lititz, which arguably added fuel to the movie’s rise as a box office smash. In fact, It director Andy Muschietti sent the girls free tickets to the movie as a thank you.

The basic facts are remarkable: thanks to a movie and a mischievous set of teenage girls, a red balloon – one with no message, logo or special features – became perhaps the most talked-about promotional product in America.

Of course, the film studio built the foundation for this: the balloon can be seen in the trailer and features prominently on the movie’s film poster. There’s magic to taking a harmless object and, by wrenching it from everyday context, turning it into a profound image of dread. Author Stephen King and the filmmakers executed the trick perfectly.

After that, the fans adopted the symbol as their own. That’s not unusual, but the surreal part is they traded on the pop-culture currency of the balloon by putting it into the real world – and in so doing, launched a promotional campaign that was completely independent of the studio marketing machine. That’s the type of brand fanaticism that marketing experts swoon over.

It also offers this one final reminder: anything, when deployed in the right way, can become a powerful promotional product.