A lesser Coen brothers movie can still be a good deal of fun. That’s the message of “Hail, Caesar!” An elaborate spoof of Hollywood movies of the early 1950s that’s also a loving tribute to them, the film is fastidiously made but terribly uneven, with some extraordinary highs, a few definite low points and lots of material at various stages in between. But particularly for movie buffs it will prove an enjoyable ride, even during the rough spots.

Josh Brolin stars as a fictionalized version of Eddie Mannix, the MGM vice-president known as one of the town’s preeminent “fixers,” suppressing unfavorable publicity about the studio’s stars. (Mannix is perhaps best known today as the man sometimes accused of arranging the “murder” of George Reeves in 1959.) The Coens’ Mannix is a man dedicated to keeping his lot, Capitol Studios, running smoothly. He also takes his Catholicism seriously—at least to the point of going to confession daily, frustrating the priest who must hear him repeatedly admit to sneaking cigarettes in violation of a promise to his wife to quit smoking), and is devoted to his family, though his job often keeps him away from his wife and son. That’s why he’s mulling an offer from Lockheed to take a management position with the aircraft firm.

Mannix constantly has crises to deal with. One involves DeeAnna Moran (Scarlett Johannsson), an unmarried Esther Williams-type star, but with a Bronx attitude, whose pregnancy he has to somehow package in a way that will make the news palatable to her fans. Another concerns problems on the set of an elegant drawing-room piece, “Merrily We Dance,” where veteran director Laurence Laurentz (Ralph Fiennes) is forced by a directive from the studio head to accept as his leading man likable but rather dim cowboy star Hobie Doyle (Alden Ehrenreich), whose way with dialogue is decidedly challenged.

But the biggest crisis centers on Capitol’s most expensive production, “Hail, Caesar!”—an epic that’s subtitled “A Tale of the Christ” (like “Ben-Hur”) but comes across like a a version of “The Robe,” without the CinemaScope. It stars Baird Whitlock (George Clooney) as a Roman general who’ll be converted after encountering Jesus during a tour of duty in Judea. As the final scenes—including his big speech at the foot of the cross—are being prepared, Whitlock is kidnapped by a cabal of unhappy Communist screenwriters, advised by none other than Herbert Marcuse (John Bluthal), who demand a hundred grand in ransom for his return.

Mannix will have to face all these challenges, and more, while fending off threats from rival gossip columnist twins Thora and Thessaly Thacker (Tilda Swinton) to print embarrassing stories, including one from Whitlock’s distant past. Naturally the various plot threads will intersect, with still others centering on handsome song-and-dance man Burt Gurney (Channing Tatum) and problem-solving lawyer Joseph Silverman (Jonah Hill) added to the mix.

Some of the picture’s set-pieces are delicious. A conference Mannix holds with a Catholic priest, a Protestant minister, an Orthodox patriarch and a rabbi about the script of “Caesar” is a nifty put-down of religious pomposity, while Johansson’s big production number, in which she’s clad in an overly-tight mermaid costume, and Ehrenreich’s sagebrush chase scene are extravagantly impressive. Both are outdone, however, by Tatum’s “No Dames,” a terrific homage to “On the Town” in which the star does some absolutely fantastic footwork. Less athletic but no less beautifully choreographed is a scene in which Fiennes’ seemingly unflappable Laurentz grows increasingly frazzled as he tries to extract a proper line reading from Ehrenreich’s Hobie. There’s also a hilarious cameo by Frances McDormand as C.C. Calhoun, a hard-bitten old editor whose career is nearly ended by an encounter with her film console.

But the material centered on the Capitol “Caesar” and Whitlock frankly doesn’t measure up. It may be a clever idea to lampoon the sort of left-leaning scribes who were treated so reverentially in “Trumbo,” but frankly the group, played by actors like Max Baker, Fisher Stevens, Patrick Fischler and David Krumholtz, doesn’t generate many laughs, and their final scene, apart from giving Tatum yet another opportunity to strike a hilariously heroic pose, is pretty flat. That adjective also applies to Hill’s cameo, in which eccentricity trumps all.

Nonetheless even when the picture isn’t working in narrative terms, you can feast your eyes on the glorious visuals—Jess Gonchor’s flamboyant production design and the art direction of Dawn Swiderski and Cara Brower, the sets designed by Greg Pasalia, Easton Smith and Barbara Mesney, decorated in eye-catching style by Nancy Haigh, and Mary Zophres’ over-the-top costumes (including some fantastic hats for the Thacker sisters)—all captured in gloriously vibrant colors by cinematographer Roger Deakins.

Then there’s the cast, which has obviously been filled with exquisite care down to the smallest roles. (You’ll need to look fast to spy Dolph Lundgren, though Wayne Knight is pretty obvious. Perhaps Christopher Lambert’s voice should have been overdubbed.) Clooney, unhappily, is far less funny than is intended—the whole routine of dim-bulb Whitlock’s becoming enamored of Marxism quickly grows tiresome—and though Brolin does his tough-but-sensitive act well, Mannix never really comes alive. The standouts are really Tatum, who sends up his own hunky persona; Fiennes, whose fussiness is goofily droll; and Ehrenreich, whose Hobie is charmingly good-natured. Johansson and Swinton aren’t far behind.

Ultimately, however, “Hail, Caesar!” impresses more as a fitfully engaging exercise than a fully realized vision. Among the collaborations of the Coens and Clooney, this falls closer to “Intolerable Cruelty” than to “O Brother, Where Art Thou?” But to render unto “Caesar” its due, the movie does deliver sporadic amusement and a few absolutely spectacular sequences. That makes it a watchable trifle—but still a trifle.