"Fame is like being in high school," goes the old talk-show quip. Everyone knows everything about everyone—dating history, drug habits, eating disorders, D.U.I.'s. Life is a tangle of cliques, crushes, grudges, and snubs. In fact, while most high schools lack million-dollar rehab facilities and screaming paparazzi, the differences between the dramedy of senior year and the private lives of Hollywood's grown-ups—particularly the male student body—are getting harder to discern.

We aren't talking about Angie versus Jen or the on-off coupling of Justin Timberlake and Cameron Diaz but about a whole new level of callow romance. We're talking about promise rings (Matthew McConaughey and Camilla Alves) and matching tattoos (Rhys Ifans and Sienna Miller). We're talking about break-ups by text, starlet booty calls, PDAs in the parking lot, and the absurdly short-sighted life commitments that are usually made only in sophomore year (Britney + Kevin 4 Eva).

"The first week that we kind of got together, he gave me a note," Jessica Alba, 26, told a reporter recently. "And [he] signed it with a dollar sign because his name is Cash." Cash Warren —get it? Isn't that cute? Thus was J and C's romantic saga—which began, ended, and presumably began again (given Alba's pregnancy) in cycles attuned to semester breaks. They were all sparked by one charmingly illustrated note whose sole message was "I really, really like you."

Let us pause for a moment. You are Cash Warren, 29, director's assistant. You are courting the star of the film on which you're toiling, a girl who happens to be the most coveted young piece of talent in the world. You give her a note that says you really, really like her. Now, in what alternative universe would this possibly work? The answer used to be: junior high. Now, it's Hollywood.

"High school and Hollywood are both about posing," says Josh Schwartz, creator of The O.C. and Gossip Girl. "High school is one big act: you don't want to get found out—that you're not cool enough, not smart enough, not hot enough—and in Hollywood it's the same thing. Plus, a lot of people in Hollywood didn't have great high school experience. This is their opportunity for reinvention and revenge."

Down in the B-through-D lists, the yearbook brought to life is even more conspicuous. There's Joel Madden knocking up Nicole Richie (the class's standard issue wayward pregnant chick.) There's the brainy music-guy, John Mayer, (hey, it's all relative) dating the former cheerleader/wannabe artsy-chick, Jessica Simpson. There's Heath Ledger canoodling with Lindsay Lohan right after he broke up with Michelle Williams (the mother of his child). There's that Beverly Hills gadabout Wilmer Valderamma, working his way through Ashlee, Lindsay, and other freshman females before joining the King of All Puerility, Howard Stern, to spill the beans on each tryst like he's reporting back to the locker room. And while he's more of an often-held-back senior, you've got to hand it to class clown Charlie Sheen, whose recent antics include crank-call voicemails to ex-wife Denise Richards ("you're a sad, jobless pig who is sad and talentless and sad and jobless and evil and a bad mom,") photos of his penis sent to women met in chat rooms, and a wedding portrait spray-painted with the caption "The Dumbest Day of My Life."