Midway through dinner and round two of drinks at Soho House Chicago, Halsey suddenly has to pee -- but she doesn't want to stop talking. From the moment she and Charli XCX sat down together, they’ve been slinging around ideas about everything from sexism in media to John Mayer’s “comedic genius” at a pace so exhilaratingly kinetic, there isn’t ever a good time to press pause.

“Should we just keep this going and talk in the bathroom?” Halsey, 22, suggests.

“Alright, let’s go do a girl pee,” Charli, 25, declares half-sarcastically.

So away we go.

Hours earlier, the two were singing the 1996 Spice Girls anthem “Wannabe” to tens of thousands of fans during Charli’s set at Lollapalooza -- a surprise performance that teased Halsey’s 30-date fall arena tour of North America, which Charli will be opening. Joining them: Canadian singer-rapper-songwriter PartyNextDoor -- whose name, it turns out, sort of sums up Halsey and Charli’s friendship. Both women love to party, and they live on the same street. Before Charli bought her $2.8 million, Tudor-style abode high in the Hollywood Hills, she scoped out the $2.2 million modernist home that Halsey eventually purchased. It’s a coincidence that came to light in March, when Halsey threw a last-minute birthday bash for producer Benny Blanco that Charli attended, and the police ultimately shut down.

“I’d just gotten the keys to the house -- it didn't even have furniture,” Halsey, born Ashley Frangipane, delightedly recalls. “Then the power went out.”

“Which I remember well,” Charli, born Charlotte Aitchison, chimes in. “Because I was doing something bad that I can’t elaborate on and was massively bummed when the music stopped.”

They have had plenty to celebrate lately. Halsey’s second album, Hopeless Fountain Kingdom, debuted at No. 1 on the Billboard 200 in June, and she scored her biggest solo hit with “Now or Never,” which reached No. 17 on the Hot 100 last month. Though the New Jersey native first found mega fame as a featured artist on The Chainsmokers’ 2016 juggernaut No. 1 hit “Closer,” she has established herself as pop’s most progressive star, outspokenly “bisexual, biracial and bipolar.” In her recent single, “Strangers,” Halsey duets with Fifth Harmony’s Lauren Jauregui about a doomed romance that happens to be between two women. “The dualities of my personality are kind of ironic, because I’m a Libra, [the zodiac sign] obsessed with balance,” she explains.

“Charli’s soul,” on the other hand, “is old as fuck,” says Halsey, alluding to the counsel Charli has brought to many other (often female) pop stars behind the scenes. In addition to her own No. 8 Hot 100 hit, 2014’s “Boom Clap,” Charli, who grew up in a suburb outside London, has written songs for artists including Selena Gomez, Iggy Azalea and Blondie. Last month, she flipped gender stereotypes in the viral music video (31 million views and counting) she directed for her critically acclaimed newest single, “Boys,” in which she cheekily objectifies a diverse group of her famous straight and gay male friends, including Diplo, Joey Bada$$ and diver Tom Daley.

“The polished pop-star thing is kind of dead,” says Charli, acknowledging the way in which both her and Halsey’s unfiltered attitude have helped transform the expectations surrounding women in their genre. Tonight, as usual, they’re impossibly cool -- Charli in a leather jacket, her curls gathered into an off-kilter ponytail; Halsey in a black bustier top, her violet pixie cut perfectly tousled -- but also exude the kind of raw personality that Spice Girls-era pop stars arguably could not.

“Part of our brand is ‘hot mess,’” says Halsey. “Being authentic. ‘Yeah, it’s 5 a.m., and I’m wasted and I’m fucking doing that.’ So if I look like shit on a certain day...”

“It’s my brand!” exclaims Charli.

“Exactly.” Halsey sighs. “OK, I’m drunk now.”

Is there anything you’re not looking forward to on the tour?

Halsey: I’m scared, because I’ve been sober on every tour I’ve ever done. And I’m not going to be with Charli there.

Charli: That’s pro, though.

Halsey: I’m neurotic. I had a really bad experience. We did Madison Square Garden and it was a sold-out show, the biggest of my career, and three songs in, everything stopped: tracks, lights, video. Everything failed, because there was one wire unplugged.

Charli: [Laughs] It’s always one.

Halsey: If I was fucked up when that happened, I don’t know what I would’ve done.

Aside from champagne, how will you be filling your time on the road?

Charli: We want to start a rollerblading squad where we all learn to skate around the arenas every day. We’re going to get the full outfit: kneepads, elbow pads.

Halsey: And then one night we’re going to blade onstage, like Blades of Glory.

Charli: I’ll be holding you up by the crotch. [Holds arms up.]

How do you cope with your bipolar disorder while touring, Halsey?

Halsey: Ummm, I don’t. Sometimes I’m just really depressed, and that’s the reality of it. But having a creative outlet for anyone with a mental illness is your best bet. I’m writing my third album on tour, so Benny and Cashmere Cat are coming, too.

Charli: Can I write with you?

Halsey: Yes! When you’re writing, how do you decide which songs to keep for yourself?

Charli: If I can see a music video with the song as it’s written, then I feel more attached to it. I was recently doing sessions with Camila Cabello, and she’s amazing. I had known her as part of Fifth Harmony, which was put together on a TV show, so I was wrongly skeptical about how much she would write. She just blew me away.

Halsey: I did a song [“Strangers”] with Lauren Jauregui from Fifth Harmony. She’s fucking dope.

Charli: I see her at parties all the time, and I’m like, “You’re a bad bitch!”

There’s a skepticism about artists who come from reality TV.

Halsey: There’s a skepticism behind female artists in general. From when I first started, I wrote [my music].

Charli: And people were like, “Oh, who wrote your songs?” There’s so much doubt, especially with being a pop star and being a female. Taylor Swift, amazing songwriter. Katy Perry, amazing songwriter. Lady Gaga, amazing songwriter.

Halsey: People want to discount them.

At the same time, there’s a lot of momentum behind women right now -- they’re championing one another.

Charli: I feel there’s a generally unspoken consensus among artists right now that it’s not cool to be competitive or fighting. It’s really about friendship and collaboration. And that sounds so fucking cheesy, but...

Halsey: No, it doesn’t. It sounds real. Charli, how do you stop the socially internalized female competitiveness from getting in your head?

Charli: That’s not in my nature. I feel like I have this reputation in the industry of being this weird outsider who stumbled in and is like, “Hey guys!” And it’s never been in my nature to fight with girls.

Halsey: The only person I’ve ever punched in the face was a dude.

Charli: Same, and it was a bad punch.

Halsey: Mine was good. In high school, I fainted in biology once, and this kid came up to me in the hallway. [Says his name.]

Charli: Oh my God, it’s on record: [Repeats the name]. We got you.

Halsey: He was captain of [an athletic] team, and he was like, “Ugh, I’m Ashley Frangipane, and I fainted in biology. I’m such a slut.” And I was like, “Say it again, and I’ll punch you in the face.” And he was like, “You heard me.”

Charli: And you did it!

Halsey: I rocked him. I almost broke his nose. We were in the principal’s office, and I felt so bad afterward. Could not be a hard bitch for more than 10 seconds. I’m really a pacifist.

Growing up, did you have mostly girl friends or guy friends?

Charli: Girls and guys.

Halsey: Mostly guys. I was gay, and I didn't know it. [I realized it] when I was 16, working at a sleepaway camp.

Charli: Like in The Parent Trap?

Halsey: Literally, yes. I had a fellow female counselor, a redhead, and we would hook up every night. We had a cabin of 9-year-old girls, [but] there was a private room for the counselors. My parents came to pick me up after six weeks, and they were like, “How are you?” And I was like, “Never been better.”

Charli: “I’m a new woman.”

Halsey: My mom was like, “So, what’s up?” And I said, “My girlfriend...” And my mom, bless her heart, didn't miss a beat. She said, “Where’s she from?” There were so many different things she could have said in that moment, and she just went with it.

Charli: Slay, Mom.

What were you guys like in school?

Charli: I was a nerd. I have that song “Break the Rules,” but that was not me. I was on time every single morning; my parents were very much about me getting good grades. But at the same time, when I was 16, I was putting my music on MySpace and getting asked to go play these raves in East London. So on the weekends, I was staying up until 4 a.m.

Halsey: I was an AP student, perfect score on my SATs, really scholarly. But then I would go to Brooklyn at night, take the train into the city. I skipped my senior prom to take acid at Sullivan Hall [in Manhattan]. That was also the first time I ever saw coke. I was like, “What are they sniffing?” I felt like I was in Skins.

Charli: Oh my God, that was me! Whenever I went to play the raves, I was like, “I’m in Skins.”

Halsey: But I think being the wallflower benefits us as artists now -- we know when to be the life of the party and when to step back. I feel like you’re always the life of the party, though.

Charli: Give me a house party any day, but on red carpets and those kind of events, I just freak out.

Halsey: I’m garbage at red carpets.

People are so critical. And tabloids are always looking for “nip slips.”

Halsey: That’s the only thing they write about.

Charli: “Halsey puts on a leggy display.”

Halsey, is there anything you wish you hadn’t been so open about?

Halsey: I wish I hadn’t spoken about having a miscarriage. Afterward, people started spamming me with photos of baby body parts and being like, “Halsey’s baby.” I had a miscarriage -- it happens to thousands of women every day. The sh--tiest part was, people by and large weren’t like, “That’s really terrible” -- everyone was like, “Who’s the father?”

Charli: But that’s just the press. I’m sure when it came to actual fans hearing that, it struck a chord. And that’s the important part.

Halsey: Weirdly enough, I think it also woman-ized me. I think everyone saw me as a kid before that.

Halsey, you started your career at 18. Charli, you started putting out music when you were 14.

Halsey: I’m a late bloomer.

Charli: [To Halsey] Oh, you’re so old. I think age isn’t really a thing in [music], which is kind of nice. [Though] there is still this stigma in the media, the idea that there’s an appropriate age to be a pop star.

Halsey: Katy [Perry] is a really good friend of mine, and I hate the way people are treating her right now. She’s evolving into a new era. As artists, we portray characters, and we deserve the right to outgrow those characters and become new ones. There’s also an expectation that we be exceptionally politically correct. And we all did shit in 2008 that we regret.

Charli: Only Rihanna has no regrets. She’s perfect. Who do you think you would have been like if you were a star in the ’70s, before social media?

Halsey: Stevie Nicks. I would have pushed the sexual limit -- that’s just my nature. Like I was saying to you in our photo shoot: “I want to be naked!”

Charli: She was like, “Is my butt out?” And I was like, “No.”

Halsey: And I was like, “I want it out.” But I think I would have been less likable, less popular [in the ’70s].

Charli: See, I don’t know. Back then, you could get away with so much more. You weren’t being scrutinized for every tweet.

How has the past year of politics affected both of you?

Charli: I never got into music to be a role model or held responsible for anything. But I’m proud to be fighting for LGBT rights and discussing feminism and the political landscape at the moment. There’s so much more of a direct connection between artists and fans now.

Halsey: It’s cool that they demand that of us -- wokeness. There’s no curtain anymore, it’s not 1999. But I think pop culture in general is a really competitive space for females. If there’s anything I want to ensure, it’s that we’re both helping each other win.

Who is the most unexpected person you’ve bonded with in your career?

Halsey: I met John Mayer at a bar. We’re like platonic mates now. If I think something is funny, I run it by him first, because he’s a comedic genius. He’ll tell me if it’s funny, but he’ll tell me if it’s not. I started answering people on Twitter by their first names. Someone will be like, “Halsey fucking sucks,” and I’ll be like, “Stacy, wow, calm down.” He loved that.

Charli: I’m going to use that.

Halsey: But I think the weirdest relationship is with Jared Leto. He’s stupidly smart. We met at Coachella. I direct my own videos, and I’ve learned so much from him about directing and acting.

Charli: You act? Dahhhling.

Halsey: I have a movie coming out next year -- I can’t talk about it.

Charli, you tweeted on your birthday that you’re planning what your coffin will look like. What’s it going to be?

Charli: I want a pink marble coffin and pink rose petals to fall from the sky whilst I get carried down the aisle. And then I want LMFAO’s “Sexy and I Know It” to play.

Halsey: I want Leonardo DiCaprio, wearing a Hawaiian shirt like in Romeo + Juliet, to speak. And I want to die in some crazy way -- like skydiving.

Charli: Have you ever done skydiving?

Halsey: You want to do it with me? Say yes!

Charli: No. I’ll push you out the plane. But I’m not fucking jumping with you.

Maybe there’s an easier way to bond.

Halsey: I’ve always had this dream of starting a band called Expensive Juice.

Charli: I have a dream of starting a band called The Tampon Girls.

Halsey: I’m in!

Charli: Cancel your tour. We’re doing this.

Halsey: PartyNextDoor: You’re off unless you want to be in the band.

Charli: He can be a Tampon Girl. [Both laugh.]

Halsey & Charli's "Badass" Fall Picks

The little downtime the duo gets on tour will be spent bumping (and reading about) some favorite artists.

1. “I cannot stop listening” to SZA’s debut album, Ctrl, says Halsey. “It’s so human, so honest. It’s about time she had her moment.” Adds Charli: ”Ugh, it is so good!”

2. “Everything Rostam touches sounds so next level,” says Charli. “His album Half-Light is going to be amazing. He is a genius and a really special person.”

3. Halsey’s looking forward to Visions of a Life, the second album from Wolf Alice: “They’re a brilliant alternative rock band with a female fronting them.”

4. “I can’t wait to hear Camila Cabello’s full album,” says Charli. “I’m super proud of the couple songs we’ve done together. She’s a great writer -- and she suggested pajama day in the studio.”

5 & 6. Charli wants to read “badass” former Hole drummer Patty Schemel’s memoir, Hit So Hard. On Halsey’s reading list? Stephen Davis’ Stevie Nicks biography, Gold Dust Woman.

How It Went Down: Halsey explains the inspiration behind "Bad At Love" (involving Sailor Moon, Romeo + Juliet, Jack Daniel's, and more):

This article originally appeared in the Sept. 2 issue of Billboard.