Hannah was paranoid—convinced that strangers were plotting her demise—and a chronic liar obsessed with men in positions of authority. She was also prone to random fits of crying. Lawrence remembers pulling into the parking lot of a CVS to buy a toothbrush one day. He returned to find her in his car with the radio set to maximum volume, blasting My Chemical Romance and sobbing in great, heaving spasms for no particular reason. None of this made Lawrence think that he should be investigating easier romantic prospects. On the contrary, he was hooked.

"It was the sort of thing where you see this wounded bird and you just want to constantly repair it," Lawrence says. "You never knew when she was going to cry and when she was going to perceive somebody to be after her. It was like the Stockholm syndrome—you become sympathetic toward your captor instead of realizing Oh my God—I'm a hostage!'"

You've dated a woman like this. In all likelihood, your friends sounded alarms that you willfully ignored. Your parents pleaded with you. Looking back, you realize that even you knew it could only end badly. She's the Crazy Girl—the one who made everyone wonder about your sanity and fear for your future. She may have taken the form of the smoky-eyed goth brooder, the tortured heiress, or the unhinged sorority girl. Whatever her identity, chances are she was intoxicatingly sexy, intense, unstable, mercurial, and impossible to be at ease around in social settings. She was completely and debilitatingly exhausting. So why the hell was she so compelling? And why are you still thinking about her?

"I think whenever you're taken by someone, be it male or female, who has the potential to lose themselves or to transform in front of you, there's something very attractive to that," says actress Parker Posey, who's played her share of Crazy Girls onscreen (Nora Wilder in Broken English, "Jackie-O" Pascal in The House of Yes, and the title role in Fay Grim, to name a few). "It has the ability to transform you. Because someone has just thrown the marbles on the floor and you don't know when they're going to do it again. It's not a relationship based on trust."

Of course it isn't about trust. This is about lawlessness. Chaos. Escapism and unpredictability—a balls-out, soul-affirming what's-nextness that is so rare and so powerful that you completely forget to give a shit about consequences and personal sacrifices. That kind of relationship has the potential, as Posey says, "to take you down roads." And whether you're the kind of guy who drives a Prius or the kind who drives a chopped-out vintage Harley, at some point, you can't help taking that ride.

"I think a lot of guys, if you've dated a bit, have the benchmarks," says Adam Fulrath, 36, an art director in New York. Fulrath's came in the form of a savant-smart, busty blonde named Sharon. Sharon painted abstract watercolors of flowers, played guitar, drank with the liver-macerating zeal of Tom Waits, and liked to drag Fulrath on spur-of-the-moment road trips to sleazy motels—and bring a camera. But her control over her tidal emotions was tenuous at best. When Fulrath finally decided he'd had enough, Sharon decided she'd get him back by showing up at his apartment in only her underwear. But it was cold, so she slipped a pair of lace-trimmed aqua panties on over her jeans, and proceeded to walk the mile from her apartment to his doorstep. Fulrath was mortified.

He immediately took her back.

"We all like danger and spontaneity," Fulrath says, eight years later. "In this attention-deficit world, where you're constantly looking around, she would keep me on the ball—she would challenge me. I was never bored with her."

Let's be honest with ourselves about what's going on here: It's an undeniable fact that if Sharon hadn't borne such an uncanny resemblance to Jenny McCarthy, as Fulrath claims she did, she would not have had the same currency to expend on her eccentricities. This phenomenon only serves to emphasize that point: Would Zach Braff's character in Garden State have sat through an elaborate hamster funeral if his hostess didn't look like Natalie Portman?

But there's a certain gloss on these big-screen depictions that leaves out a key component of the Crazy Girl appeal: The closer to the edge she skates, the more enchanting she becomes. There is a gulf of difference between the quirky (She wears a helmet! She likes the Shins!) and the mad (Oh, fuck, oh, fuck. She's cutting herself again.)—a place inhabited by self-damaging ticking time bombs like Amy Winehouse. This is a dangerous place. It's in these rocky outcroppings that we find ourselves contemplating what it might be like to crash at a roadside motel with Lisa Marie Nowak, the diapered astronaut charged with attempted kidnapping. For your average repressed, career-driven shlub, the terra incognita that these women represent seems vaguely—liberating.

"I think underlying it all is sex," says David Rabe, playwright and author of Hurlyburly. "The sexual state seems more present, more up-close in that type of woman. There's something in that disheveled personality that says they're going to make that state more available somehow—deeper and more intense.

Long after Lawrence has shaken Hannah's spell, and his mom has confessed her secret fear that his muse would have one day "suffocated the children" had they ever gone down that road, he still can't stop thinking about her.

"[All the girls] I've met since her, in some way or another, have been the most spectacular girls on earth," Lawrence says. "Before I met Hannah, I would have died for any one of them. I met this girl who was a commentator on cable news—super-brilliant, very cute. We got into this relationship, and I all of a sudden found myself thinking, Why isn't she doing it? Why isn't she enough for me? I mean, this girl is successful, makes hundreds of thousands of dollars, travels all over the world, has half the U.S. Senate in her Rolodex, and that's not enough. Because she's not crazy."