When Brennan McDermott was an underclassman at Simsbury High in Connecticut, he found himself in a timeless situation, familiar to watchers of horny 1980s comedies and after-school specials alike.

“A couple of my buddies were like, ‘Hey, let’s go to the bathroom,’” said McDermott, now Simsbury’s senior class president. “I was like, ‘Whoa, what’s going on here?!’ I got kind of uncomfortable with it. They were all passing it around. I didn’t take it.”

In a modern twist from the coming-of-age canon, though, “it” wasn’t a cigarette. It was a small, rectangular vape product known as the Juul.

In the public imagination, vaping — with its oversize, multipart manipulatable products — has become associated with a techier, dweebier slice of the population. But as early as 2015, e-cigarette use by high-school and middle-school students had eclipsed cigarette use.

And by late 2017, an informal consensus had burbled up from students, teachers, parents and the internet: All across the country teenagers who in generations past would have become cigarette smokers — or, perhaps, would never have taken up smoking — were falling in love with the Juul.

“Cigarettes, they’re not even a factor anymore,” McDermott said. “Nobody smokes cigarettes. You go to the bathroom, there’s a 0 percent chance that anyone’s smoking a cigarette, and there’s a 50-50 chance that there’s five guys Juuling. And it’s like, how Band-Aid has become synonymous with ‘bandage’? Juul has become synonymous with ‘vape.’”

Created by two former Stanford University design students, the Juul attempts to mimic the nicotine hit of a real cigarette, and sells for $49.99. Over Christmas, Nielsen reported that Juul had achieved a 46.8 percent market share — exceeding the top market share reached by Marlboro cigarettes at the peak of that product’s measured success. Then, last month, Nielsen said Juul had 54 percent of the market.

I, an adult, first noticed the Juul on the various Instagram feeds of the unapologetically dumb Barstool Sports. In recent months, they’ve been flooded with college kids finding creative ways to display their prowess with, or devotion to, their Juuls: kids hitting their Juuls at their parents’ dining room table over fall break; kids hitting their Juuls in the hospital after a bloody drunken escapade. It was all a bit bewildering.

It took oodles of efficient pop-culture manipulation for America to accept cigarettes as the ultimate symbol of rebellious cool. But now, all of a sudden, a vape is cool?

Sebastian and Gio, students at a continuation high school in Northern California, both use a Juul. “I’m on probation so I can’t smoke marijuana,” Gio said, by way of explanation. (The students asked that their last names not be used, for fear of disciplinary infractions.) “And I don’t want to smoke cigarettes. Cigarettes taste nasty.”

Sebastian said: “I like the feeling of it. The lightheadedness. It makes me feel sober and high at the same time. Plus it looks sleek — you smoke it, you look kind of bougie.” Both are also fans of Juul’s flavored tobacco pods. In particular, Gio said: “Mango! That Mango go hard.” (Other flavor options include Cool Mint, Fruit Medley and Creme Brulee.)

As for discretion, Gio said: “It looks like a USB drive. It doesn’t look suspicious.”

Chidum Okeke, 18, of Louisville, Kentucky, said, “In my opinion it looks like the coolest thing ever. Almost futuristic.” Okeke doesn’t Juul, but he has gone a bit viral tweeting about it.

He traces the inflection point to early 2017. That is when the “Juul wave,” as some have called it, started to go from the popular-kid set in his grade to entire neighboring schools. “It’s so small, so easy to hide in the palm of your hand,” he said. “And they’re rechargeable! I’ve lost track of the number of people I have found charging their Juuls in class through their laptops. It’s almost comical.”

Okeke said he also knows kids who have named their Juuls; names he has heard include “Juulia” and “Richard.”

In February, Greta Frontero, an 18-year-old senior at Westfield High in New Jersey, wrote an article for her school paper about the Juul.

It is a true gem of reportage: “A senior male was caught Juuling during class when his chemistry teacher’s back was turned. ‘I took a hit of it and blew it in my sweatshirt, but the smoke came out the back of my jacket,’ he said. ‘When my teacher asked why there was smoke coming out of my jacket and I opened my mouth to respond, more smoke came out of my mouth.’”

“It’s almost like a game,” Frontero said. “Like if the teachers would catch you doing it or not.” But it’s not just school, she said: At house parties, Juuls are so rampant that theft has become an issue.

That’s where customization has come in.

“I’ve seen nail-paint polish, initials carved in, smiley-face stickers,” Frontero said. “It’s really just to make sure that if someone steals yours you know it’s yours. And they’re everywhere. You’re in someone’s basement and the host doesn’t even know you’re doing it ‘cause they don’t smell.”

For the record: At least in Westfield, kids use a different product, wax pen vaporizers, for smoking weed. The Juul is strictly for tobacco.

After her article came out, Frontero said, “the teachers had to catch up.” Now kids at Westfield are getting handed three-day suspensions for Juuling. Gio, from Northern California, agreed that “teachers are starting to see what they really are.”

So have kids started carrying actual USB drives, just to throw teachers off the scent? Gio laughed. “Not yet!”

And getting a Juul is as easy as ever.

“My friend has a middle-school brother and they walk into Krauszer’s” — a local New Jersey grocery store — “and buy it without any question,” Frontero said. “It’s ironic. This product was made to wean addicts off cigarettes, and in reality, it’s attracting teenagers who would never smoke.”

The glamorization of the cigarette took place over decades and throughout countless Hollywood movies and glossy ads. The Juul iconicity was birthed much faster: through social media. That includes personal accounts, teenagers eager to fuel the Juul wave with winkingly knowing tweets about the hype cycle.

With more cynicism, Barstool Sports and other youth-targeting brands have jumped on the bandwagon, too. Arya Toufanian is the 25-year-old proprietor of I’m Shmacked, a Girls Gone Wild-style roving party and video series.

“We started to post Juul stuff maybe six months ago, and we started getting submissions right away,” Toufanian said. “You can tell immediately when a product is viral.”

I’m Shmacked then paired the Juul with another recent teenager obsession.

“We made fidget spinners out of Juuls,” Toufanian said with pride. “We thought, you know, people are holding Juuls all the time anyway! A university student built a render, and we 3-D-printed it. It was kind of a grass-roots project in a way.”

“One of the things I’m super-interested in is meme culture,” said McDermott, the Simsbury High class president. “What resonates with our generation is the memes. I haven’t seen the Juul on TV. But you’ll see a bunch of memes about Juuling. It’s just, like, making it more socially acceptable — it’s perpetuating the thing that vaping is cool.”

Ashley Gould, the chief administrative officer of Juul Labs, is careful to walk a line between pride and responsibility. “We’re the No. 1 e-cigarette in the United States,” Gould said. “And we’re not a big tobacco company. We’re an independent company.”

Pointing out she is not a smoker, Gould ticked off some of the properties of the Juul that the company believes have made it big: the way the “formation of the e-liquid mimics the way the nicotine is delivered in a cigarette”; the fact that Juul was the first to “design an e-cigarette that was not cylindrical.” But, she added, “what we’ve seen happening with youth we did not want to be happening.”

“We’re taking it extremely seriously,” Gould said. “We do not want underage kids using our products. Our marketing is directed toward adults, tested with adults. And I do think it’s worth noting: All of the things you see on social media, we have absolutely nothing to do with. We actively try to take these things down. But unless there’s an infringement of our intellectual property it’s quite difficult.”

So the teen love caught the Juul team off guard?”Yeah,” Gould said. “I think that’s a fair statement. We’re actively trying to understand it so that we can combat it — but I can’t tell you that we currently understand it today.”

Recently, memes and health fears have collided: now kids are going viral by warning each other to stop Juuling. In February the Twitter user @MateaCannavino collected screen grabs of messages purportedly from friends of friends diagnosed with Juul-related diseases. (Her commentary: “The Juul wave is ~over~.”)

“A few weeks ago there was a whole thing going around that it caused lung cancer. And for probably, like, a day people were like, ‘I’m going to stop doing it!’” Frontero said, and laughed. “And then that quickly faded. I don’t think anyone’s all that concerned.”

So can anything stop this youthful fandom? Perhaps the only hope to end the teenagers’ winking love of the Juul is to expand the demographic out of its hipness. To that end, I’m doing my part. On a recent winter evening, a buddy and I walked out of a show and into a surprisingly pleasant Thursday evening in Manhattan. We’d just seen Yung Lean and Thaiboy Digital, two delightfully strange international musicians, and we were buzzing.

It was one of those latish, drunkish weekday nights that had the potential to become a properly late, properly drunk weekday night. In fact, in a few minutes, we’d find an Irish bar and drink more, fast. But first my buddy wanted to smoke.

In the past, in times like these, I might bum a cigarette or two or seven. Instead, he took out a small square vape.

Here we were. A couple of grown men. Hitting the Juul.