OMG: BTS is on “SNL” tonight.

K-pop boy band sensation BTS is making its much-anticipated musical guest debut with host Emma Stone on “Saturday Night Live,” and diehard devotees have been lined up outside 30 Rock since Monday in hopes of scoring last-minute tickets.

And it’s not just tweens.

“It normally starts Friday, this is insane” Jill Goucher, 28, tells The Post of the usual time people start waiting for limited standby seats. She and her pal Amanda Scott, 32, commute from Virginia, and have been camping out every Friday for three years. Neither has ever witnessed an army of fans start waiting for tickets this early.

“The things we do for BTS,” 16-year-old Gaby, who has been sleeping on the street outside NBC Studios since Tuesday, tells The Post. She and her two besties skipped three days of the 10th grade in hopes of snagging a chance to see their favorite group perform live.

“Our teachers know that we’re here,” says Gaby’s friend, Lucy. “They’re like, ‘text your friends so we know you’re OK.’”

For those who haven’t been sleeping on the street all week in anticipation, there’s no other way to acquire tix to the show. Even the campers have no guarantees. The number of passes released Saturday at 7 a.m. is dependent on a number of non-public factors, including how many seats the artists themselves reserve for family and friends. Line veterans say it’s usually only 100 or so.

But sometimes there are fringe benefits.

“We’ve met two of the [BTS] songwriters,” says Cassie Crisp, 22, who took a 15-hour bus from Ohio with friend Megan Iler, 19, and has been sleeping on 48th Street since Monday evening. Crisp says even they’ve befriended a number of fellow fans in line. Thursday night, when BTS’ new album dropped, “pretty much everybody stayed up streaming,” she says.

So, why all the hype? Here’s a rundown of what to know about the supergroup:

By the numbers

That BTS has turned Rockefeller Plaza into a campsite for adoring fans is hardly surprising for those familiar with the group’s fandom: The band’s YouTube account has 23 million subscribers, and their Instagram and Twitter accounts have more than 16 million and 19 million followers, respectively.

The group’s third hit record, “Love Yourself: Tear” reached number one on the US Billboard 200 in May 2018, the first K-pop album to do so. In December, the single “Fake Love” became the most-streamed K-pop song ever on Spotify — where the BTS catalog has already hit the five billion stream mark.

The group is in the 2017 Guinness World Records for the “most Twitter engagements” by a music group, and their take on Drake’s #inmyfeelingschallenge was the most-liked tweet of 2018.

Since dropping their latest release, “Map of the Soul: Persona,” its lead single “Boy With Luv” has already racked up more 33 million views as of this writing.

“We all woke up at 5 a.m. and you could hear screaming,” 18-year-old Leslie Huynh, who counts herself as roughly 40th in line for standby tickets, says of the moment the album dropped.

At the time, BTS owned nearly every top trend on Twitter.

BTS essentials

The group, also known as the Bangtan Boys, was formed by record label Big Hit Entertainment in 2013, when the members were teens and tweens. They’ve been living with each other ever since.

The seven-member group is composed of Min Yoon Gi (Suga), Jeon Jung Kook (Jung Kook), Kim Seok Jin (Jin), Park Ji Min (Jimin), Kim Tae Hyung (V), Kim Nam Joon (RM) and Jung Ho Seok (J-Hope), aged 21 to 26, and all born and raised in South Korea. Jung Kook, the group’s youngest member, is considered its lead vocalist. RM is the group’s only fluent English speaker.

Mattel recently announced a collection of BTS dolls inspired by the bandmates — which some fans deemed “creepy.”

As for what’s next, the group is still striving for a few unachieved dreams. “A Hot 100 and a Grammy nomination, these are our goals,” RM tells Entertainment Weekly.

5 songs to know

“Boy With Luv”

“Idol”

“Fake Love”

“Boy In Luv”

“Blood Sweat & Tears”