This has pretty much all my movie-star boyfriends in it. Yes, I’m excited.

You’re either going to love or loathe Zach Galifianakis when he puts himself into Todd Phillips’ hands. In The Hangover, Galifianakis’ borderline-pedophiliac, mentally challenged man-child was annoying enough to sink the movie. (Yes, the most successful R-rated comedy of all time does have some detractors.) And in Due Date, Galifianakis plays a gentler version of more of the same. His Ethan Tremblay is a 23-year-old (!) aspiring actor with a pocket pooch and the demeanor of a 6-year-old.

This time, at least, he’s occasionally funny instead of just irritating. In Phillips’ follow-up to his box-office smash, Ethan’s the thorn in an expectant father’s side from the time they meet disastrous at an airport. Peter Highman (Robert Downey Jr.) is trying to get back to Los Angeles in time for the birth of his first child. Ethan, meanwhile, is trekking to “Hollywood” to pursue his ain’t-gonna-happen dream. A car accident, bag mix-up, and light tussle on the plane gets both of them on the no-fly list, and with Peter’s wallet buried in his confiscated luggage, he has little choice but to accept Ethan’s offer to drive cross-country in his rented car. Near homicide, naturally, ensues.

Four scripters (including one responsible for the horrendous Made of Honor) results in a tone that’s all over the place: There’s dark humor, light Odd Couple-esque squabbles, and, when all original ideas seem to have been exhausted about halfway through the film, strenuous wackiness a la car crashes and ridiculous schemes. Galifianakis is more likable here than he was in his breakout Hangover role–Ethan’s insistence on sticking to rules, such as not letting anyone touch your luggage in an airport, is mildly amusing–but it’s Downey Jr.’s wry, tightly wound, foul-mouthed bitterness that earns the best and sometimes surprising laughs. (Bet you never thought you’d giggle at a grown man punching a kid in the gut.)

Running jokes such as a coffee-can urn and that damn dog lose their bite quickly, though, as does the film overall. What started out as an inspired coupling turns into another hate-you-love-you buddy flick, a moratorium on which is long overdue.

Jungle fever

Tropic Thunder may have first appeared on your radar last August, when Owen Wilson dropped out of filming after his suicide attempt. Or maybe you heard about it earlier this year, when word got out that Robert Downey Jr., in the film’s movie-within-a-movie, would be playing a black character.

But the premise for this Hollywood-skewering war spoof has reportedly been roller-derbying around writer-director Ben Stiller’s brain since 1987. That’s 21 years spent marinating in the comedian’s twisted psyche, eventually co-molded by scripters Justin Theroux and Etan Cohen and, certainly, further shaped by an A-list cast that includes Jack Black, Nick Nolte, Steve Coogan, and Danny McBride.

The result? A comedy beast that’s nearly impossible to dissect. At least not without giving up the goods, anyway. Whereas the details about Downey’s racial transformation, for example – his character, Kirk Lazarus, is actually an Australian actor so celebrated and Method he’s hired to portray an African-American soldier in a Vietnam flick – might have comprised 75 percent of the gag in lesser hands, here the concept is a mere launching point for a performance so brilliant, it’s fair to regard Lazaurs as August’s Joker. Another not-so-secret cameo may help rinse the ick off a superstar’s recently tarred reputation. (Though, in my opinion, not quite.)

There are fake trailers, surprise violence, layers upon layers of film-industry mockery, and rampant offensiveness that’s attracted cries for boycotts from more than one activist group. You can hear Stiller’s diligence to his vision in the dialogue: “More stupid!” demands a villain who takes the director’s character, Tugg Speedman, hostage and orders him to re-create one of his broad critical flops. He complies, delivering this nugget as a mentally challenged man talking about bad dreams: “This head movie makes mah eyes rain!” Earlier, Lazarus discusses craft with Speedman, declaring that his commitment to the aforementioned part must have left him feeling “moronical.”

The thing about moronicality is that it takes loads of intelligence to get it right, and in this regard Tropic Thunder can sidle up to classics from Some Like It Hot to The Jerk. For all its comedic density, the plot is simple: A memoir by Four Leaf Tayback (Nolte), Vietnam’s Pvt. Ryan, is being adapted to the big screen by clueless British director Damien Cockburn (Coogan). He can’t control his cast, which besides Lazarus and action-hero Speedman includes rapper-turned-actor Alpa Chino (Brandon T. Jackson), drug-addled star of Eddie Murphy-esque franchise The Fatties, Jeff Portnoy (Black), and still-level-headed newcomer, Kevin Sandusky (Jay Baruchel).

Tayback suggests that Cockburn “take them off the grid” to scare the artistes out of his actors and elicit more believable performances. But Cockburn’s orchestrated dumping of his cast into the jungle for a guerrilla shoot goes immediately wrong, and soon well-armored poppy farmers assume the actors are DEA agents. The thespians’ survival skills kick in – eventually – as they try to fight their way back to the world of gift bags and Booty Sweat (Chino’s energy drink).

Unlike last week’s Pineapple Express, Tropic Thunder’s blood-and-guts angle is introduced early and graphically, so its combination of action and yucks never feels disingenuous. All of the big players have ace moments – even Matthew McConaughey,who took over Wilson’s part as Speedman’s agent – but Stiller and Downey steal it: Stiller’s Speedman is a superior Derek Zoolander, hilarious whether he’s wriggling his body while dramatically taking bullets or quietly going nuts in captivity.

And it’s all of 30 seconds before Downey kills, in this case in his character’s trailer, without even uttering a word: Dressed as a monk – and still white – his expression during the preview’s narration is a dead-on imitation of every pretentious performance ever captured onscreen. As far as his guttural delivery and mannerisms when “black,” it’s too thorough, ridiculous, and well-plotted to be offensive (and Chino calls Lazarus on it repeatedly for good measure).

Speedman’s “Simple Jim” character – with buck teeth and a peroxide Prince Valiant cut — isn’t as excusable. But the script’s ingenious argument of the drawbacks of an actor “going full retard” — as well as the movie overall – will make your eyes rain.

 Because I’ve already written about 20,000 words this week but want to get these stories out, I’m doing a little linkage today:

–Steven Spielberg is reportedly building a social-networking site for Dennis Kucinich and other people who’ve spotted UFOs.

–Here’s a story on Ben Stiller’s upcoming Tropic Thunder…including a photo of Robert Downey Jr.’s apparent Al Jolson impression. Can’t wait to see what the folks who bitched about Fred Armisen doing Barack Obama are going to say about this.

–The Onion made a movie. 

–Speed Racer is going IMAX. I’m ridiculously excited for this movie, even if I don’t see it on a billboard-size screen.

Bueller?

If Ferris Bueller had gone to class or if Rushmore’s Max Fischer included ­doctor-shopping among his extracurricular activities, they might have turned out a whole lot like Charlie Bartlett. It’s impossible to watch the titular character of director Jon Poll’s feature debut without recalling those nerds-of-the-people who’ve gone before him. Another decade, another atypical-and-yet-attractive teen hero, another message about the importance of being true to yourself.

Of the two films, the occasionally entertaining and well-intentioned Charlie Bartlett apes Rushmore most closely. When Charlie (Anton Yelchin) is tossed out of yet another private academy for selling fake IDs, his wealthy, dippy mother (Hope Davis) enrolls him in a public school. He insists on taking the bus instead of employing the family driver on his first day but still wears a suit, never considering that this uniform might keep him from achieving his goal of rock-star popularity. (In the opening scene, Charlie fantasizes about an arena-size crowd chanting his name.) Naturally, he’s mocked by the masses and beaten up by Murphy (Tyler Hilton), a thug who takes offense to his briefcase. “Actually, I believe it’s an attaché case,” Charlie tells him. And naturally, Charlie finds a way to win them all over, but not without acquiring a nemesis: Principal Gardner (Robert Downey Jr.) is a formerly happy history teacher and currently self-loathing alcoholic who keeps an eye on Charlie, though he’s less concerned that he’ll violate school rules than his foxy daughter, Susan (Kat Dennings).

In his first feature script, Gustin Nash wedges a lecture about prescription-drug abuse within the genre’s usual it’s-OK-to-be-different message. Charlie’s ah-ha moment comes after his mother immediately sends him to a psychiatrist (whom she, a Klonopin-popper herself, has on call) after his unsuccessful debut at school. The doc doesn’t hesitate to prescribe Ritalin. And after Charlie discovers for himself what a few of those babies can do—suddenly he can’t stop studying, cleaning, or running outside in his tightie-whities—he decides to sell the pills at a dance. Instantly, girls are running topless and boys are wrecking and rioting. The next day Charlie is treated like a champion—albeit one the students assume could get more drugs. So he starts a bathroom-stall psych service, listening to kids’ problems and then rattling off each of their symptoms as his own to every knee-jerk prescriber in town.

Charlie Bartlett’s initial fun at the expense of the uncontrolled use of controlled substances can be off-putting depending on your mind-set and tolerance of exaggeration for the purpose of satire. Obviously, the main side effect of a dose of Ritalin isn’t tearing your clothes off. And it’s supposed to be touching when Charlie tells Kip (Mark Rendall), a truly depressed misfit who doesn’t have a friend in the world, that according to his research, no one has ever died from a panic attack. But then he soothes Kip with pills, which have obviously killed plenty. Nash’s script does eventually address overdose—though only by downing a bottle, not the lesser-known and therefore arguably greater danger of mixing the wrong prescriptions at the wrong time—but it feels like too little, too late after all the junior-­psychiatrist yuks.

The film is more successful, ironically, when it sticks to tried-and-truisms. Charlie hears some heartbreaking stories: the quarterback who’s sick over the fact that he secretly can’t stand football, for example, or the cheerleader who’s afraid to say no to horndogs. Even the clichéd daddy-letting-go-of-his-daughter struggle feels genuine here, mainly because Nash doesn’t let things get too sugary. (When Gardner all but calls Susan a slut in his misguided attempt to have a conversation about not letting boys take advantage of her, it’s shocking but realistic.) The cast, too, helps elevate the movie above standard teen fare. You may find Yelchin’s wide-eyed Ferris impression annoying, but his Charlie is earnest and exuberant, believable as a natural leader despite his quirks. Charlie’s mother, too, isn’t terribly likable, but Davis’ breathy, space-cadet portrayal is exactly what you’d expect from a perpetually altered lady of leisure. Downey Jr. isn’t showy here, but anyone who knows his history will wince at a scene in which Gardner bottoms out. Like Charlie’s classmates, you’ll likely be skeptical when the film introduces itself—and then surprised when you’re won over by its small charms.