Here's the plot: the story of a bunch of actors, lost in the jungle and beseiged by drug-runners led by a twelve-year-old boy, who are filming the story of a bunch of soldiers lost in the woods and beseiged by Viet Cong. The film stars Ben Stiller, Jack Black, Robert Downey Jr., Jay Baruchel, Brandon T. Jackson, Danny McBride, and Nick Nolte. It features supporting roles by Matthew McConaughey, Tom Cruise, Steve Coogan, Bill Hader, and cameos by others. It was written by Stiller, Justin Theroux, and Etan Cohen, and was directed by Stiller. We got that out of the way? Good. Because here's the deal: "Tropic Thunder" is funny. And smart. How often do these go together, nowadays? They used to, back when Mel Brooks was running the show, and it's popped up again here and there, with "Knocked Up," "40 Year Old Virgin," and "Forgetting Sarah Marshall." But "Tropic Thunder" has something all those movies don't: A point. The message isn't just about Hollywood, either; it's something about all of us, who pretend to be what we aren't. It's human nature to make believe; it's human nature to give into those beliefs and think they're real. Okay. Enough philosophy. I'm putting my soap box away. "Tropic Thunder" is absolutely gut-bustingly hilarious. It's also highly offensive, crude, and over-the-top; there are jokes that go to far, there are jokes that don't go far enough. Such is the nature of comedy. My point is, even the few jokes that fall flat serve to make the rest of the movie all the better. And it doesn't hurt that the film evokes the best from its three headliners: Stiller has never been funnier (I'm not a huge fan of his, but I have to say, the man approaches, in this film, something akin to comedic genius); Jack Black, likewise, is in top form (again, I'm not a big fan; but here, he's absolutely terrific); and Downey is, simply a wonder to behold. With all due respect to the rest of the cast and crew: This film would not be what it is without Downey's presence. It's not that he's portraying "a dude disguised as a dude pretending to be another dude" (in this case, a white Australian actor playing an African American); it's that he portrays it so eloquently. You never doubt his authenticity, a method actor so lost in his role that he doesn't drop character until after he does the DVD commentary. The entire cast is hilarious; Downey is also thoughtful and intriguing. "Tropic Thunder" is not for the faint of heart, or those who like their jokes clean, or those who like their movies without much thought put into them (if "Norbit" is your idea of classic comedy, please leave now). "Tropic Thunder" is a comedy with equal parts heart and cojones. It'll rock you out of your seat (especially with it's seventies rock soundtrack). It'll make you laugh 'til you wet yourself. And, certainly, it will make you re-think the way comedies are being made these days. If only all comedies could look this good, or be this thoughtful, or make us laugh this hard. If only.