Small time New York crook Harry Lockhart (Robert Downey Jr.) is having a surreal couple of days. After some late night Christmas “shopping” at a toy store leads to the shooting of his partner and being surrounded by the police, the basically decent guy (who just happens to be a criminal) suddenly finds himself in the middle of a big-time audition for a major Hollywood production. Next thing he knows, Harry’s suddenly in the middle of a huge Los Angeles party hobnobbing with the rich, famous and the in-betweens all in preparation for a screen test that could launch him to super-stardom.

To help with the audition, the producer sets him up with tough guy private eye Perry van Shrike (Val Kilmer), affectionately known as “Gay Perry” to his friends, a ruthless and narcissistic detective charged with giving Harry firsthand knowledge of the street. He’s fussy. He’s nasty. He likes things a certain way (and gets brutally upset if they change). He also doesn’t like Harry, not in the least bit, smelling trouble on every inch of this sad-sack wannabe thespian’s badly tailored suit. He’s also gay. But, then, to quote Jerry Seinfeld, “Not that there’s anything wrong with that.”

Like any of this really matters. Soon the duo find themselves mixed up in a murder mystery surrounding a failed starlet’s (Michelle Monaghan) apparently suicidal sister, a wealthy producer’s (Corbin Bernsen) missing heiress daughter and a mystifying dead body that somehow makes it out of the trunk of a floating car and into the bathroom of Harry’s hotel. Faster than you can say “hard-boiled,” corpses are falling from the sky, doubles are continually crossed, fingers are severed humorously from their limbs and those who appeared to be one thing turn on a dime to actually be something completely different. It’s a mess, and unless Harry and Gay Perry can find a way to work together – and stop lying – both of them are going to end up in the morgue with a toe tag.

“Kiss Kiss, Bang Bang” is the ridiculously nihilistic and bloody entertaining directorial debut of “Lethal Weapon” and “The Last Boy Scout” screenwriter Shane Black. It’s an absurd, over-the-top bullet-riddled action-thriller-comedy with its tongue stuck so firmly in cheek anyone taking even a second of it seriously should be immediately sent to a psych ward for observation. In all honesty, this movie is a farce, an almost Mel Brooks style parody of the very type of buddy blow’em up action extravaganza Black (along with his producer Joel Silver) helped create. But it’s also a heck of a lot of fun, almost embarrassingly so, the whole thing covered in a gloss of Mike Hammer and Philip Marlow veneer so thick some viewers will start licking it up like syrup.

In some ways, it’s very similar to Robert Rodriguez and Frank Miller’s early year hit “Sin City” in that Black’s film is another case of style over anything even remotely substantive. Sure this one is missing the cool hyper-realistic black and white imagery and unadulterated energy of that one, but what “Kiss Kiss, Bang Bang” lacks in CGI pyrotechnics it certainly makes up for it in both character development and pacing. Through all the whip-snap rat-a-tat-tat dialogue and almost continuous thunder of smashing glass and profanity laced one-liners, Black remembers to write two highly memorable and idiosyncratic characters in Lockhart and Perry.

Of course, that wouldn’t mean a thing if both Downey and Kilmer didn’t make the grade with their performances. Thankfully, they do, both rising so far as to make both their characters instant classics. Kilmer hasn’t been this loose, this relaxed and – wonder of all wonders – funny in what seems like an eternity. Stuck in bad movie, “Mindhunters,” after bad movie, “Alexander,” after bad movie, “Red Planet,” for what seams like the entire last decade, Black’s script revitalizes the actor bringing him back in touch with his humorously self-aware side we haven’t seen since cult favorites “Real Genius” and “Top Secret!” put him on the map. But Downey’s even better, taking a repulsive bottom-feeder like Harry and turning him into a slovenly schmuck impossible not to love. He’s a hoot, an idiot savant lying his way through life until little things like the combination of a bullet, a missing finger and a sexy old friend wakes him up to the fact being a good guy might actually be worth the effort.

Don’t get me wrong, the picture has its share of problems. Monaghan follows up her strong turn in “North Country” with a whiny and forgettable one here, while clips of Bernsen in his younger days is far more compelling than anything he’s doing onscreen in this. Also, for as complex and intricate as Black’s Mickey Spillane-like mystery is, the solution to the whole thing is astonishingly simple. Silly, too, and the more I think about it the more it annoys me that the writer-director couldn’t turn off the whimsy just for a second and write himself a little better climax.

But he can’t, and after a while you either get used to the idea “Kiss Kiss, Bang Bang” is nothing more than a loudly obnoxious juvenile comedy of male bonding, swear words and bloodshed, or you stand up and leave the theater and go see what else is playing next door. I chose to accept, remaining in my sear and chortling loudly with every R-rated bullet hole splattering blood and political incorrectness across the screen. Black successfully takes apart the action film, reassembling it into an asinine comedy of errors and redemption that easily ranks as one of 2005’s most wondrously entertaining guilty pleasures. It shoots from the hip, takes no prisoners, and, with a bang, delivers everything it promises. How many other features this year can claim that?

Film Rating: êêê  (out of 4)