To my mind, Tropic Thunder (2008) is the boldest, strongest, and flat-out funniest comedy that Ben Stiller has directed. While it satirises an easy target – Hollywood excess – it does so in such a savage and unrelenting fashion that on some levels it seems a surprise that Stiller and his production team were allowed to get away with it all. Then again, considering the star power involved here – Ben Stiller, Tom Cruise, Robert Downey Jr, Jack Black, Matthew McCounaghey, et al – it sometimes feels less like biting the hand that feeds it and more like the hand somehow biting itself. It is gloriously self-aware. I honestly think this is one of the best American film comedies of the past 20 years.

Stiller plays action star Tug Speedman, whose attempts to secure critical acclaim beyond his commercial blockbusters are ending in miserable failure. When he signs on to star in the true-life war epic Tropic Thunder, he and his pampered co-stars make a mockery of the production until their director takes them deep into the south-east Asian jungle to shoot the film guerilla-style. The director steps on a landmine, the cast are left in the wilderness without rescue, and a clueless Speedman continues to act his way through a genuine incursion into the territory of a criminal narcotics factory.

Pretty much everything that comprises American film culture comes under fire in Tropic Thunder. It mocks superstar vanity projects, the silliness of method actors, the drive of comedians to be taken seriously, and Hollywood’s overriding obsession with re-telling true stories. It covers the inability to let go of the Vietnam War, the ridiculous luxury of studio film shoots, rich people’s addictions, and the arrogant control of the industry by vain, thin-skinned egomaniacs. Above all it skewers Hollywood’s broken attitudes to race, gender, sexuality, and social justice. All of that, and straight-up comedy too.

The film cleverly introduces its cast via a short series of fake movie trailers, each of which establish the leading cast and their backgrounds: bland action star Tug Speedman, scatalogical comedian Jeff Portnoy (Jack Black), award-showered ‘legitimate’ actor Kirk Lazarus (Robert Downey Jr), and aggressively masculine rapper Alpa Chino (Brandon T. Jackson). The pointed satire of each sequence is sharp; it both introduces characters and sets up jokes for later in the film.

While Stiller plays the nominal lead, the comedy is balanced well between each of the lead players. It also finds room for a raft of entertaining supporting players including Jay Baruchel as the one serious actor of the lost cast, Danny McBride as a fire-obsessed effects worker, Nick Nolte as the grizzled veteran whose life is being adapted to film, and Matthew McCounaghey as Speedman’s dedicated agent and manager.

Following the crisis from Los Angeles is Hollywood studio head Less Grossman, played enthusiastically by megastar Tom Cruise in what is probably the strangest role of his entire career. Clad in a fat suit, bald cap, and weirdly massive prosthetic hands, his hysterically over-the-top portrayal represents an amalgam of every high-stress, over-confident, hair-trigger-temper media mogul in California. It is immediately funny because it is Tom Cruise, who has perpetually maintained a public image as a warm and friendly individual, but beyond the against-type casting it’s funny because it’s genuinely funny. To describe Grossman as one of Cruise’s best-ever performances feels oddly like an insult, but I properly mean it. This film stands up alongside the likes of Magnolia and Born on the Fourth of July as some of his finest work.

While it is odd to see Cruise occupying such an exaggerated and theatricalised role, it is jaw-dropping to see Robert Downey Jr ducked out in curly-haired wig and blackface as Kirk Lazarus. It is the boldest gambit of the film, and miraculously avoids most accusations of racism through two means. First: the screenplay – by Stiller, Justin Theroux, and Etan Cohen – situates Brandon T. Jackson’s Alpa Chino as a constantly critical Greek chorus, bringing up every aspect in which Lazarus’ behaviour is unacceptable. Secondly: Downey Jr performs the role to the fullest possible extent. He commits entirely to the joke, exaggerating the offence to such a degree that no viewer is left with any resentment at all.

The satire is en-pointe, but more importantly Tropic Thunder is simply enormously funny. While the film seems overwhelmingly male, so too does the industry it ridicules. The cast, the story, and the technical presentation are all fantastic. Downey scored an Oscar nomination for his work, which is rare enough for a comedy performance. The entire production honestly deserves nothing less.