“Man,” says Robert Downey Jr’s Kirk Lazarus, “I don’t drop character ’til I done the DVD commentary.”

Guess what? Downey don’t drop character ’til he done the cast commentary, alongside out-of-character Ben Stiller and Jack Black.

Good gag? Sure. Conceptual, like. Except no matter how often Lazarus says “Everyone shut up” whenever he’s on screen, the execution isn’t as funny as the pitch...

Same goes for Tropic Thunder. Hopes were high for Stiller’s first directing gig since Zoolander.

The plot is trampled terrain: Tinseltown twits making a war movie get dumped in an Asian jungle and have to fight for survival.

Stiller recycles his pouting pillock routine as Tugg Speedman, failing action stud. Black’s Jeff Portnoy is fat.

Some jokes nail the target: Lazarus’ “full retard” speech kills and Tom Cruise’s producer hits an agreeably grotesque groove.

But Portnoy’s drug issue? Rapper Alpa Chino’s (Brandon T Jackson) sexuality? These gags don’t miss their target – they never had one.

High gag count, mixed value. Quantity takes precedence over quality on the extras, too. Extended improv footage? Hit fast-forward.

Far better is Rain Of Madness, a mock-doc presented by Jan Jurgen (Justin Theroux) detailing the disasters in the making of the movie within the movie.

Rain might even have made a wittier film – Thunder’s overkill turns a satire of a big-budget misfire into something dangerously close to a bigbudget misfire.

That added layer of irony surely wasn’t intended.

Kevin Harley