A famous actor makes an unbilled appearance in a small role toward the close of Gore Verbinski’s romantic comedy-thriller “The Mexican,” and he does a thoroughly professional job. There’s nothing special to the part, though, and it could have been played equally well by any number of fellows whose faces and names few of us would recognize. So the question arises: why the cameo? The answer seems to be nothing more profound than that the actor thought it might be fun and the filmmakers knew it would give the audience an easy kick: “Hey, isn’t that…?” And that’s precisely the problem with the whole film. It’s not that “The Mexican” is terrible; the male half of the leading couple refers to what’s he’s suffered over the course of the plot as a “long debacle,” but it would unfair to apply that phrase to the picture. Indeed, the flick has its share of quirkily amusing moments, and the performers appear to be enjoying themselves–something that engages the audience, too. But it’s one of those films that, while sporadically pleasant, never really achieves critical mass. Though likable enough in a rather dowdy, rumpled way, it’s too fractured and structurally slipshod to amount to much, and so ephemeral that it passes out of the consciousness almost as soon as it unspools. You’ll probably walk out of the theatre feeling reasonably good, but unable to remember a great deal about what you’ve just seen, and not caring either.

“The Mexican” is basically a loopy road picture, but oddly enough–given its pairing of Brad Pitt and Julia Roberts–the superstars share remarkably little screen time, being separated through most of the labyrinthine plot. Pitt plays Jerry Welbach, a decidedly laid-back and physically clumsy fellow who’s accidentally forced into performing a service for a now-incarcerated mob boss and assigned to travel south of the border to retrieve a priceless revolver (the “Mexican” of the title) for the fellow. Jerry’s girlfriend Samantha (Roberts) objects most strenuously, saying she’ll leave him if he goes off without her; but the poor schmuck sees no alternative, having been threatened with death if he refuses. So Jerry makes his way to Mexico, where his natural ineptitude and bad luck soon get him into trouble involving local robbers, the police and a variety of other colorful characters. Meanwhile Samantha is taken hostage by a gunman named Leroy (James Gandolfini), who’s apparently been assigned to keep her under wraps as insurance that Jerry will complete the job. Most of the picture deals alternately with Jerry’s increasingly frustrating experiences in doing what’s expected of him and Sam and Leroy’s gradual development of a sense of camaraderie and mutual respect; as part of his journey, Jerry is exposed to a variety of mythic descriptions (all delivered in surrealistic flashback) about how the fabled gun came to be, while on her side Samantha becomes a kind of romantic advisor to the captor-hitman, whose predilections turn out to be rather different from what one might expect. This might all sound quite benign, but the picture has a distinctly seamy side, too: the action is repeatedly punctuated by gruesome killings and a succession of double-crosses and twists that don’t mesh terribly well with the fluffier moments. (The intricacies of the plot, which once more show the seemingly ubiquitous influence of “Charade,” are also occasionally inexplicable: at one point a major character simply disappears without explanation, presumably for no better reason than that the scriptwriter had no further need of him, and the denouement is virtually incomprehensible.) The apparent intent was (with all due respect to Gandolfini) to replicate on the big screen the combination of light and dark that “The Sopranos” has managed on the small one. Unfortunately, neither scripter J.H. Wyman nor helmer Verbinski (whose sole previous effort was the heavy-handed techno-farce “Mouse Hunt”) has the dexterity to bring off so delicate a balance. As a result “The Mexican” careens so uneasily from slapstick to violence to froth to suspense that you’ll probably end the ride feeling a bit car-sick.

Nonetheless the malady doesn’t prove fatal, largely because the cast is so game. Pitt proves an amiable goofball, managing to keep his character sympathetic even after we see him doing some pretty awful things. Roberts is compelled to rant too much and too often–shrewishness doesn’t really become her–but she’s unmistakably a star, working well with both Pitt and Gandolfini, who brings the same mix of authority and bemusement to Leroy that he regularly invests Tony Soprano with. There are eye-catching supporting turns from Bob Balaban in a decidedly uncharacteristic role as a mob lieutenant whose sharp tongue and smooth manner make him a threatening figure indeed, and Richard Coca, who brings a welcome geniality to the part of a roguish car thief. I won’t reveal who the surprise guest star is at the close; but at least it’s not Gary Oldman again.

The good news about “The Mexican,” therefore, is that it gives its stars some nice opportunities to showcase their talents, and isn’t unbearable. The bad news is that structurally it’s as clumsy as its bumbling hero, and its multiple shifts of tone may leave you a more than a little queasy by the close.

F

Last year Warner Brothers released “My Dog Skip,” one of the best canine flicks of recent years. (It ranks right up there with 1996’s charming “Shiloh.”) Now, apparently to restore the balance in the universe, the studio is offering one that’s equally awful. “See Spot Stink” would be a more appropriate title for this mangey mongrel of a movie.

“Spot” is a gross-out buddy comedy centered on a doofus mailman (David Arquette) who becomes pals not only with a super-smart government-agent pooch that’s run away from a witness protection program and is pursued by both mobsters out to kill him and his FBI partner, but also with a rubber-faced tyke (Angus T. Jones), the son of his dream girl, single mom Leslie Bibb (who’s off on a business trip and spends most of the movie trying desperately to get home and retrieve the kid from Arquette’s irresponsible hands). The trio, needless to say, get involved in a succession of slapstick situations and endless chases, alternating with long stretches of stickily sentimental bonding among man, child and dog. The big joke is that the mutt is brighter and more capable than the guy he teams with; the sad fact is that he’s a lot smarter than the writers (no fewer than five of them, headed by George Gallo, the perpetrator of the recent bomb “Double Take”), director John Whitesell (a TV veteran who stages the picture as the alternately frantic and syrupy sitcom it is) and the human stars, too. Simply put, the movie is pitched to the lowest possible level. There haven’t been this many violent pratfalls in a single picture since all those horrible John Hughes “Home Alone” clones, and the bonding between Arquette and Jones is so calculated and smarmy that it could provoke in viewers the same sort of violent stomach disorders from which the duo occasionally suffer themselves. As if that weren’t bad enough, the movie periodically features the vilest ethnic stereotypes (not only comic Italian mobsters but a shrieking Oriental taxi driver and a bulbous black sidekick for Arquette).

In fact, the whole movie is so flat and filled with dead spots (pun intended) and noxiously tasteless bits of business that the only way you can stay alert and sane is to try to gauge which performer embarrasses himself most grotesquely in it. Arquette’s certainly a strong contender: he’s humiliated endlessly, in sequences that force him to play “gotcha” with an assortment of pooches, dance like George Jefferson and E.T., spit out great gobs of bran flakes and prunes, and simulate being struck repeatedly by powerful electric charges. But whether Arquette is sufficiently sentient to feel actual embarrassment over all this is unclear. After all, this is the fellow who starred in “Ready to Rumble.” And he apparently wasn’t frightened off by a script which required him, at one particularly gruesome point, to roll about in dog-doo clad only in a wet undershirt and shout, “I’m covered in caca!” One would think a line like that might give an actor pause in taking a role, but not Arquette; he’s obviously beyond the possibility of embarrassment.

That leaves us with the large supporting cast. Bibb is in the running: she’s repeatedly splattered with mud and involved in one particularly hideous gag centered on a zebra’s flatulence (don’t ask)–pretty scary stuff. Then there’s Michael Clarke Duncan, as Spot’s partner, who blubbers at the thought of being separated from the canine and, at one point, must exhibit a literally frozen rictus of a smile. And we can’t forget Joe Viterelli and Steven R. Schirripa, as the inept mob hitmen who pursue the dog and, like a bargain-basement version of Joe Pesci and Daniel Stern, get clobbered in a series of slapstick confrontations with him. Or Anthony Anderson, who sputters and chortles endlessly as Arquette’s African-American postal pal and, in one memorable scene, does a painful split in an attempt to grab a five-dollar bill with his buttocks.

But despite all this powerful competition, the winner in the embarrassment sweepstakes is surely Paul Sorvino, the distinguished father of an Oscar winner no less, as the gangster who’s out to snuff the title mutt. Apart from having to play scenes in which he barks out orders to his minions, (in one memorable instance while stuffing himself with tortellini and gnocchi), Sorvino must endure being chomped by Spot in the most delicate area possible not once but twice–so that by the close he’s been surgically provided with a pair of ball bearings that clink as he saunters down a jail hallway and his voice has gone up several octaves, leaving him to sound like a counter-tenor at best (a strange fate for a guy who has actually aspired to become an opera singer). Everybody involved in “See Spot Run” comes off badly, but Sorvino is the most brutally demeaned.

We can close these dispiriting observations by noting that two characters each raise the same question at different points in this dismal movie, which is quite unconscionably aimed at a kiddie audience. “What’s that smell?” they inquire. Viewers who have the misfortune of stumbling into this “Spot” will certainly be able to provide the answer.