Still glistening with post-show sweat, Pete Wentz -- bassist, lyricist and designated pretty face of Fall Out Boy -- strides through a grim backstage hallway. "I better say goodbye now," he warns, heading out of the squat brick building that houses tonight's venue, a club in Manchester, England. "It's gonna be hectic with all the fans outside." He pulls a bright pink scarf tightly around his neck, pushes a heavy door open and braces for mass adulation.

Outside, it's the kind of Manchester evening that moved Morrissey to pen morose lyrics about fat girls: Rain falls in frigid drops from a single, endless gray cloud. There are all of three kids hanging out behind the Manchester Academy, and not one of them even glances at Wentz. He's taken aback for a moment, then breaks into a homecoming-king smile. "Look at this," he says, gesturing at a nonexistent crowd. "Is this Beatlemania or what?"

Wentz isn't delusional -- he's just in the wrong country. Eight days earlier and 3,000 miles away, a chorus of high-pitched voices screams "Pete!" As Wentz, 26, hustles toward the side entrance of MTV's Times Square studios, he pauses to face his public: a giggling group of junior high school girls wearing braces and North Face jackets. "I'm gonna give every single person here a hug!" he announces. The girls swarm him, ponytails flying, as they snap cell-phone pictures destined for purple-bordered MySpace pages.

A year ago, Wentz and his band -- an emo-ish pop-punk quartet from the wealthy suburbs of Chicago that took its name from the sidekick to Bart Simpson's favorite superhero, Radioactive Man -- were an indie act known only to skateboarding Warped Tour kids. They seemed unsuited for mainstream success: Their singer, Patrick Stump, was a music geek who hated the spotlight; Wentz was borderline suicidal, OD'ing on his anti-anxiety meds as they recorded their first major-label album.

But then came "Sugar, We're Going Down," perhaps last year's catchiest rock single and certainly its most unintelligible, as well as the Sixteen Candles-inspired video for "Dance, Dance" and a marketing strategy that takes its cues from hip-hop (Wentz has his own clothing line, record label and protege acts). Now Fall Out Boy are pop stars, with a double-platinum album (From Under the Cork Tree, due for a March 14th re-release with five extra tracks), a spring arena tour and nearly 800,000 friends on MySpace.

Wentz is visiting TRL today to accept a plaque commemorating the "retirement" of the "Dance, Dance" video after fifty days on the show's countdown. The audience unleashes hormonal shrieks as Wentz walks onto the set, wearing a red hooded sweat shirt from his clothing line. Backstage, the grizzled road crew of the day's other musical guest, prog-rockers Coheed and Cambria, is unimpressed. "Oh, I love him," a roadie sneers. "He's my favorite!"

* * * *

In a cramped tour bus parked outside the Manchester Academy hours before showtime, Patrick Stump is yanking a striped polo shirt away from his belly. "I'm horribly uncomfortable with being the frontman," Stump says, looking horribly uncomfortable as he sits Indian-style on a leather couch. His endearing look combines mutton-chop sideburns, thick glasses, an ever-present hat and a slight paunch. "With Pete, I get to be the anti-frontman," he says. "There's not attention on me; I just get to sing. Pete loves photo shoots, and I fucking hate them. Of all the things I have to be self-conscious about, my looks are top of the heap."

While he is unlikely to seek a male-modeling contract, Stump, 21, is his band's musical engine. Wentz e-mails him huge files of lyrics that Stump puts to music, playing bass, drums and guitar on demos made with Apple's GarageBand. "I guess Patrick is some kind of genius -- he's a total mad scientist," says the band's shaggy-haired lead guitarist, Joe Trohman, 21. Trohman first met Stump in a Borders bookstore when they were both high school juniors in 2001; after checking out the songs Stump had posted on MP3.com, Trohman and Wentz decided his high, pure tenor was perfect for the poppy group they were forming.

Stump wrote "Sugar, We're Going Down" in about ten minutes. He admits to deliberately slurring Wentz's lyrics to "make them sound better." (A much- circulated Internet parody transcribes one garbled line as "lonely dark cock that's going and pulling." The actual lyric, for the record, is "A loaded God complex/Cock it and pull it.") "I was trying to do a straight punk song for fun," Stump remembers. "And I saw those lyrics and just kind of barked them out. But there was something about the rhythm of it, where I was like, 'Hmm, that actually might be too good for just a shitty punk song.'" After recording his vocals for the tune, Stump turned to Andy Hurley, 25, the band's intense, bespectacled, vegan drummer. "He was like, 'Yeah, I just got your kid's college tuition paid for,'" Hurley says.

The son of a folk singer turned corporate drone, Stump is the sole band member without any tattoos and the only one without ties to the local hardcore scene. Instead of playing basement shows, he spent most of high school in his bedroom, obsessing over music. "That's what I did instead of making out with chicks," he says. "I didn't have girlfriends or anything." His strongest memory of his parents' divorce is carrying his father's records out of the house. He learned a lot of songs from his dad, which was a mixed blessing. "It's sort of gross to watch your dad sing -- kind of guttural and passionate," Stump says. "It's almost like watching him bone."

The other guys in the band name-check the Smiths, Pantera, Slayer and hardcore bands you've never heard of, but Stump big-ups jazz guitar virtuoso Joe Pass, John Prine, Tom Waits, the Small Faces, Prince, Jackie Wilson, Christina Aguilera, Ornette Coleman, Taj Mahal, Abba and Earth, Wind and Fire, among others, in the course of an hour. He drops his voice an octave into an eerily accurate impression of Elvis Costello singing "New Lace Sleeves." "My Costello thing helped me a lot in Fall Out Boy, because he has that element of 'Yeah, I'm singing this really catchy pop song, but the lyrics are really negative,'" he says.

Stump bounds off after the conversation winds down, grateful to escape the attention. In contrast, it's hard to get Wentz to stop talking. He's been in therapy for a while, and it seems like his shrink doesn't have much trouble getting him to open up. Wearing his pink scarf and a black hat covering his red-and-black-striped hair, Wentz settles into a worn sectional sofa in the club's dank dressing room. A bulletin board on one wall is emblazoned with graffiti left by bands like Sepultura; a huge marker drawing of a hairy penis covers another wall. The room smells faintly of ancient sweat.

Wentz ignores the ambience and seems to enter a trancelike state, answering questions with compulsive honesty over the course of three and a half hours. The twenty-six-year-old son of a law professor and a private-school admissions dean, Wentz was a soccer jock who dove into hardcore in his teens, becoming a local celebrity in the scene. He gave himself his first tattoo during class one day when he was fourteen, digging into his ankle with a pin dipped in India ink. The black "x" is still there -- it looks like it hurt.

When Wentz plugs his clothing line, Clandestine Industries, and record label, Decaydance, he sounds more like a rapper than a rock star, and that's no accident. "Rock guys are like, 'Fuck, I don't want to do stuff like that.' But look at the state of rock music," he says. "Bands can't sell fucking records. The new rock stars are dudes like Jay-Z." He wants Fall Out Boy to be "a culture. You're going to eat, sleep and breathe it. I want it to be a way you think about the world." And he's frank about his motives for signing bands like the FOB-sound-alike Panic! At the Disco to his label. "People are going to be piggybacking bands off of us," he says. "Somebody's going to be pulling those strings, why would it not be me?"

Wentz's verbose, angsty lyrics about making out, breaking up and hating yourself account for much of the band's teen appeal. Many of his songs are about one on-again, off-again girlfriend. But an argument last year ended with him punching out a car window, and they split for good in October. He's moved on and now speculates about dating one of his many celebrity crushes. "We talk sometimes, me and Ashlee [Simpson]," he says. "I mean, I think she has a boyfriend or whatever, but we talk. She's gorgeous."

But for all his drive, entrepreneurial verve and elaborate grooming -- his pre-show primping involves a straightening iron that needs a thirty-pound industrial converter to work overseas -- Wentz is wracked with insecurity. "I feel confidence in myself, but at the same time there's these cracks in the facade and those little things underneath that are unstable," he says. He takes Xanax every day to calm an anxiety disorder and pops Ambien to sleep. And in February 2005, he may have tried to kill himself. Sitting in a Best Buy parking lot in Chicago, he took so many Ativan pills that he collapsed and had to be hospitalized for a week.

Wentz refuses to call it a suicide attempt but doesn't know what else to term it. "I was isolating myself further and further," Wentz says, speaking softly and slowly. "And the more I isolated myself, the more isolated I'd feel. I wasn't sleeping. I just wanted my head to shut off, like, I just wanted to completely stop thinking about anything at all." His eye contact with the ceiling is intense as he admits to a fascination with the suicides of Elliott Smith and Joy Division frontman Ian Curtis. "It's so hard to think about and understand. I'm not making an argument for being a disturbed genius; I was a confused kid," he says. "I felt like I was being Pete Wentz for everybody else, and I didn't have Pete Wentz to turn to."

While Wentz recuperated, the rest of the band was forced to do a brief U.K. tour with a substitute bass player -- which is harder than it sounds, since Wentz supplies all of their stage banter and much of their showmanship. But in the end, his absence boosted the other guys' confidence. "We couldn't latch onto Pete, so we had to grow some balls and, like, talk on our own onstage," says bleary-eyed, jet-lagged guitarist Trohman, fresh from a four-hour afternoon nap.

The metalhead son of a cardiologist, Trohman used his bar mitzvah money to buy his first half-stack. He's the only Jewish guy in the band (his Smiths-themed tattoo violates Talmudic law) and the only one who's not straight-edge. During a 2003 trip to Tokyo, Trohman started drinking, and he's partial to weed now, too. "I smoke a decent amount," he says. "This is gonna sound like a total fuckin' pothead's logic, but it helped me put some things in perspective." The last year has offered a lot that needed to be sorted out. "It's like, 'Go do this thing, go do that thing. Go to Fuse, go to MTV,'" says Trohman, who's dating a college student from back home. "It's not just like, 'Here you go. Here's a million dollars.' All of this stuff is awesome, but it's tiring."

* * * *

By the time he steps onstage a couple of hours later, Trohman is finally awake. He matches Wentz's pogo-ing energy (apparently undiminished by Xanax), leap for leap. It's a short but fiery performance, with an audience of sixteen-year-olds screaming along to every word.

Afterward, back in the dressing room, the four guys hang out, relaxed but pumped up in post-performance bliss. Stump, for some reason, breaks into an impersonation of Christopher Walken's lines from Annie Hall, while Wentz happily munches cookies. Stump eyes the snack. "I gain weight if I eat an apple," he says with a sigh.

A few minutes later, in the middle of a dorky discussion of the merits of the Fall, Pere Ubu and Mogwai, I find myself humming a snatch of "Sugar, We're Going Down." Everyone stares. "Dude, what were you just singing? Was that Superchunk?" Stump asks. "Nah, he was totally humming part of 'Sugar,'" Wentz says, grinning in triumph. "See: There's the bands that you say you like to sound smart, and there's the bands you say you like to get laid. And then there's the bands you really listen to."