Remember that Christmas Eve when you looked excitedly under the tree and discovered the big present in the shiny wrapping paper had your name on it?

Remember how you spent the entire night, feverishly imagining all of the wondrous treats that could possibly be inside the box, then hurriedly tearing off the paper the next morning only to find something you didn’t want?

You’ll experience that same sickening disappointment during Ben Stiller’s latest directorial offering, which unites some of Hollywood’s finest comic talents (Jack Black, Robert Downey Jr and Stiller himself) in a slam-bang satire of war epics including Apocalypse Now, Platoon and Full Metal Jacket.

Tropic Thunder promises so much but fails to deliver, burdened with a flimsy screenplay and an irritating turn from Black as a jittery heroin addict, who attempts to go cold turkey by asking his co-stars to tie him to a tree.

We’re extremely tempted to leave him there.

The film’s wrapping – a fake advertisement for an energy drink called Booty Sweat and a trio of bogus trailers – is by far the most enjoyable part of the show.

First up is action superstar Tugg Speedman (Stiller) looking buff in his latest brain-dead, post-apocalyptic sequel, Scorcher VI: Global Meltdown.

Next comes rotund comedian Jeff Portnoy (Black) in an assortment of grotesque body suits to portray the various family members from The Fatties, Part 2.

Last but not least is a promo for Satan’s Alley, a gay love story involving Benedictine monks, pairing five-time Academy Award winner Kirk Lazarus (Downey Jr) and MTV Best Kiss award winner Tobey Maguire (playing himself with tongue wedged in cheek).

Within the opening 30 minutes of Tropic Thunder, we wish that we were watching any of these three ‘masterpieces’ instead.

Using a simple film-within-a-film conceit, the main feature introduces us to inept British director Damien Cockburn (Steve Coogan), who watches in horror as his big budget war opus, penned by Vietnam vet John ‘Four Leaf’ Tayback (Nick Nolte), spirals out of control.

With obnoxious producer Les Grossman (Tom Cruise) on his back, Damien takes extreme action.

He strands his pampered stars – Tugg, Jeff, Kirk, Kevin Sandusky (Jay Baruchel) and rapper Alpa Chino (Brandon T Jackson) – in the jungle, hoping to capture the raw fear as they battle the elements for real, augmented with pyrotechnics courtesy of special effects wizard Cody (McBride).Unfortunately, the actors stumble into the domain of bona fide drug lord (Brandon Soo Hoo), who thinks he is witnessing an American invasion.

Life imitates art imitates life as the cast takes on a well-armed militia with only prop weapons and method acting to save them.

Tropic Thunder takes aims at the image-obsessed film industry but barely hits the soft targets.

Stiller plies his usual schtick while Downey Jr steals every scene as the blond, blue-eyed Australian thesp who undergoes a skin pigmentation procedure to convincingly portray a wisecracking African-American sergeant.

‘I don’t drop character until I done the DVD commentary,’ he boasts.

Method acting in extremis.

Downey Jr also snags the script’s most cutting, near-the-knuckle monologue, explaining why an actor should ‘never go full retard’ if he wants to snaffle an Academy Award.

War, what is it good for? In the case of Stiller’s film, almost nothin’.

• Release Date: Friday 19 September 2008
• Certificate: 15
• Runtime: 106mins

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