Ben Stiller, left, and Robert Downey Jr star in Tropic

This is the one they put on Ben Stiller’s tombstone.

This is the spectacular spectacle that he will be known for, the movie that all those years spoofing Hollywood, the industry he grew up in and the people who run it, were leading up to.

Tropic Thunder is Ben Stiller’s “Apocalypse Now.” After this, nobody will dare make another Vietnam War epic. After this, the sound of choppers, the slang and the POW camps will just be punch lines. After this, nobody will ever say “Tom Cruise has no sense of humor.”

Stiller rounded up a cast of A-listers, took them to Hawaii and blew up $90 million worth of stuff. He made a movie about making a movie that no movie-maker should ever have made. And it’s a riot.

There’s the dim-witted action star (Stiller) who still smarts that he’s never been good enough to win an Oscar. “Load and Lock!”

There’s a Beyond Method Aussie actor, a five-time Oscar winner (Robert Downey Jr.) who has undergone “pigment augmentation” (blackface) in order to play, essentially, Ving Rhames.

There’s a drug-addicted tubby funny man (Jack Black) who hates himself and a world that won’t take him seriously.

There’s a kid (Jay Baruchel) just starting out, and a rapper-entrepreneur dabbling in acting (Brandon T. Jackson).

And their in-over-his-head director (Steve Coogan), egged on by a deranged ‘Nam vet (Nick Nolte), dumps these Blackberry babies in the jungles of Vietnam to get “Blair Witch”-style realism, real suffering.

This part of Southeast Asia still has armed men fighting wars over opium. Real guerrillas, armed to the teeth, face real Hollywood phonies, armed with blanks, not realizing that they’re not in a movie. A Platoon of funny people left Missing in Action – “Tropic Thunder” is lowdown high camp, a movie lover’s comedy.

Downey goes deep, deep, to play this pretentious thespian acting out an African-American cliche. Stiller, Nolte, Black, Coogan and Danny McBride, as a gonzo movie pyrotechnics guy, all score. Tom Cruise, in fat suit, bald cap and fake furry arms, sends up foul-mouthed Hollywood power players as a studio chief trying to cuss his way out of a jam.

There’s so much exposition to get through that the movie can drag at times.

But this is Stiller’s magnum opus, a brilliantly broad character farce that should do what Stallone and all his steroids never could: end the Vietnam War, the Hollywood version anyway.