Slick but superficial, Jodie Foster’s comedy-drama about stock market manipulation feels slightly behind-the-curve, but it’s buoyed by a couple of genuine star turns. It doesn’t pack the punch of a film like “The Big Short,” but “Money Monster” is entertaining enough, though ephemeral—you probably won’t remember much about it once the credits stop rolling, but until then you’ll have a pretty good time.

The retrograde quality is established early on as Lee Gates (George Clooney) is introduced as the caddish, fast-talking star of the eponymous show on a cable news network, one clearly modeled on Jim Cramer’s CNBC program “Mad Money,” which was actually in its heyday some years ago. Dispensing financial advice with unabashed showmanship—he enters each episodes in outrageous costumes, gyrating in consort with a couple of groovy dancers—Gates recognizes both the clout and the vacuity of his pontifications, which he delivers with manic energy and cheesy certitude. Meanwhile his long-time producer Patty Fenn (Julia Roberts) keeps things from running off the rails from her console in the control booth.

Gates is currently embarrassed by the collapse of a stock called Ibis Clear Capital, which he’d pushed as a sure winner for months. Its value shrunk astronomically when the company announced that $800 million of its funds had inexplicably disappeared as the result of a computer glitch. Ibis CEO Walt Camby (Dominic West) has abruptly pulled out of a scheduled interview with Gates, but his communications director Diane Lester (Caitriona Balfe) is ready to serve as a replacement.

The day’s plans go out the window, however, when an interloper crashes the set—Kyle Budwell (Jack O’Connell), a lower-class schmuck from Queens who’s lost everything he inherited from the sale of his late mother’s house in the Ibis disaster. Blaming the show—as well as the company—for his misfortune and brandishing a gun, he takes Gates and his crew hostage, demanding that the company provide a real explanation for the stock’s decline. To add to the threat he outfits Gates with a vest rigged with explosives, ordering that the station keep them on air for the duration. Soon a police squad commanded by Captain Powell (Giancarlo Esposito) has surrounded and evacuated the building, while Lester tries desperately to contact Camby, who’s virtually unreachable while jetting around Europe. Her efforts are obstructed by company CFO Avery Goodloe (Dennis Boutsikaris).

The premise of the screenplay by Jamie Linden, Alan DiFiore and Jim Kouf bears an unfortunate resemblance to that of “John Q,” the 2002 Denzel Washington vehicle about a man who took over a hospital emergency room after an insurance company refused to pay for his son’s heart transplant. But while that movie made the mistake of treating the idea with grim seriousness, “Money Monster” is comic from the get-go. And although some of the attempts at humor go awry—a bit about the show’s producer Ron Sprecher (Christopher Denham) going entirely too far testing an erectile-enhancement cream is both crude and unfunny, and another focusing on some zonked-out hackers falls flat—for the most part they work, especially a priceless sequence in which Emily Meade appears as Budwell’s pregnant girlfriend Molly. The hostage team brings her to the studio—following the usual protocols—to talk him into surrendering, but things don’t unfold at all as they expect.

Clooney and Roberts carry the picture ably in the first half-hour, and Foster keeps the momentum strong, aided by ace cinematographer Matthew Libatique and editor Matt Chesse. To be sure O’Connell disappoints; his previous films (especially “’71”) have demonstrated his potential, but here the bluster never convinces and the accent sounds forced. (In all fairness, the character is poorly written: Kyle is meant to come across as sympathetic, but he’s such a dolt it’s hard to care much about him.) But with good supporting turns from the likes of Lenny Venito as Lenny, the crew’s dedicated cameraman, the pitch remains high.

Unhappily, the energy level dissipates in the film’s latter stages, when Gates actually begins to act like a journalist and throws in his lot with Budwell. The picture has already introduced some feeble criticism of the public’s fascination with crisis by cutting away to crowds watching the unfolding drama on TV, but when the two men venture out onto the street to walk toward a confrontation with Camby, and are greeted by cheering throngs along the way, the tempo slows to a crawl, and recollections of “Dog Day Afternoon” and other similar films force one to make invidious comparisons. Nor does the final revelation about the fate of that missing $800 million carry much of a jolt; in fact, it seems pretty anticlimactic, even—like Gates’s show itself—a bit over-the-hill in terms of how advanced financial skullduggery works nowadays, though the YouTube references at the close are amusing enough.

If in the end “Money Monster” proves more of an agreeable star vehicle than a sharp social statement, however, Clooney and Roberts show that they’re still capable of shining in the cinematic firmament, counterbalancing their recent stumbles (Clooney in “The Monuments Men,” “Tomorrowland” and even “Hail, Caesar!” and Roberts particularly in “Mother’s Day”). As with so many studio contract players of yesteryear, their presence proves sufficient to make even a shallow piece like this fitfully diverting.