As your mind wanders during the formulaic, witless, self-contradictory piffle that is "Showtime," you may ask yourself questions. Like: Remember when Robert De Niro's presence in a movie used to mean something?

De Niro movies weren't all great, but they almost always were significant, almost always were trying to do something more than sell tickets.

De Niro's recent move toward lighter material isn't necessarily a bad thing. His cold, imposing image was calcifying until his comedic skills - displayed in limited quantities in "Brazil" and "Midnight Run" - fully blossomed in "Analyze This" and "Meet the Parents," both of which have sequels in the works.

Now he comes across as much more of an everyday guy, which is fine, but given that his company is producing many of his movies these days - including "Showtime" - you'd think he'd make time for something substantial amid "The Adventures of Rocky & Bullwinkle," "Flawless," "Men of Honor" and "15 Minutes."

Also: Remember when Eddie Murphy used to be funny?

You don't have to go too far back. That animated donkey in "Shrek" was a stitch, and the first "Nutty Professor" was a tour de farce, though the sequel was just a tour de farts.

But Murphy as a reckless, loudmouth police officer is a concept that lasted two "Beverly Hills Cop" movies too many, and the idea of making such a cop plum dumber isn't the twist required.

The premise of "Showtime" is that Mitch Preston, the tough-as-nails cop played by De Niro, and Trey Sellars, the goofball officer played by Murphy, are forced to become partners while a reality-TV crew, led by a go-get-'em type, Chase Renzi (Rene Russo), trails them to create a weekly series.

Trey, a wannabe actor held back by his glaring lack of talent, is gung-ho about the face time, while the grumbling Mitch cooperates only because his boss ordered him to. Mitch, you see, had exposed the L.A. Police Department to a possible liability suit by shooting an intrusive video camera during an attempted bust, and the opportunistic Chase leveraged permission for the series as a settlement.

"Showtime" might as well be called "Rerun" for all of the repackaging it's doing. De Niro recently played a cop in an anti-media satire, "15 Minutes," and he previously starred in "Wag the Dog," a definitive skewering of Hollywood's influence on reality, and vice versa. Meanwhile, Murphy played the followed-around-by-cameras game in the Steve Martin comedy "Bowfinger."

The scenes that introduce Mitch and Trey show some promise: Mitch sternly lecturing a classroom of little kids about the difference between real and movie/TV police work, Trey hitting every cliche the cop-flick handbook at a failed audition.

But rather than expanding on these points, director Tom Dey ("Shanghai Noon") and the script (credited to Keith Sharon, Alfred Gough and Miles Millar) just pretend they never were made. You watch "Showtime" dumbfounded as it hammers the entertainment business and media for imposing phoniness on real life - all while presenting a "reality" of stupid car chases, big explosions and dumbed-down plotting and banter.

It's no coincidence that Mitch and Trey's big case involves tracking down a villain with a mega-gun that makes things blow up spectacularly.

To the filmmakers, satire is just an attitude to be copped. From the moment the stupid media types start thrusting their cameras in De Niro's face, you know where every so-called joke is headed. Chase declares that in America, "everybody wants to be on television." Well, shiver me timbers.

The thinness of the conception gives the actors so little room to maneuver that they turn in uniformly one-note performances. De Niro perpetually looks like he just sat on his gun, while Murphy apparently decided the way to sell his unfunny lines was to raise his voice.

Russo's Chase has been conceived as a user-friendly version of Faye Dunaway's ruthless TV executive in "Network"; you're supposed to think she's cute and spunky. She's thoroughly annoying.

The filmmakers toss in the suggestion of a romance between Chase and Mitch but are too lazy to flesh it out. They no doubt figure we know the drill and can fill in the blanks.

De Niro must participate in a lame gag in which he parrots other famous cop-movie lines, such as "Go ahead, make my day," and "Do you feel lucky, punk?" Yes, the filmmakers resisted the temptation to include "You talkin' to me?" No, they couldn't resist sticking James Brown's beyond-cliche I Got You (I Feel Good)" on the soundtrack.

The movie also features William Shatner playing himself as the TV show's director, thus enabling him to refer repeatedly to "T.J. Hooker" and to complain that De Niro's character "is the worst actor I've ever seen." At least Shatner's self-parodying priceline.com ads were free.

"Showtime," which should have the identically named cable network suing for defamation, ends on a cheesy freeze-frame and includes outtakes over the credits. They're not funny either.

A criminal waste of talent.

1 star
"Showtime"

Directed by Tom Dey; written by Keith Sharon, Alfred Gough, Miles Millar; photographed by Thomas Kloss; edited by Billy Weber; production designed by Jeff Mann; music by Alan Silvestri; produced by Jorge Saralegui, Jane Rosenthal. A Warner Bros. Pictures release; opens Friday, March 15. Running time: 1:35. MPAA rating: PG-13 (action violence, language and some drug content).
Mitch Preston - Robert De Niro
Trey Sellars - Eddie Murphy
Chase Renzi - Rene Russo
Captain Winship - Frankie R. Faison Himself - William Shatner

Mark Caro is the Chicago Tribune movie reporter.