Thor

For a holding maneuver, “Thor’’ itself turns out to be diverting enough — not close to a sharp-edged romp like “Iron Man’’ but not the B-movie roadshow some of us were expecting. Call it a B+ movie. (On a side note, the movie was shot in 3-D but you can barely tell, even in the Asgard scenes that are meant to suggest vast CGI distances. This isn’t bad 3-D, just completely unnecessary. If you want to save money and stick with the flat version, you won’t miss a thing.) The film’s chief weakness is that star Chris Hemsworth isn’t Robert Downey Jr. in quickness or charisma, but that really won’t matter to the film’s primary constituencies: young boys, older fan-boys, and women.

As to the latter, not for nothing does the film see its Norse demigod hero through the eyes of Jane Foster (Natalie Portman), the plucky astrophysicist who happens to be standing by in the desert when Thor crashes over from the parallel-realm of Asgard. (The preferred mode of travel for Norse demigods, by the way, is tornado. Don’t expect this movie to play well in Alabama for quite some time.) In one early scene, the hero removes his shirt to reveal the torso of an Aryan Chippendales dancer and it’s played as a Taylor Lautner moment for older gals: Portman’s Jane goes quietly gooey, as does her sardonic intern (Kat Dennings as a sort of Facebook-era Eve Arden), as did a vocal contingent of the women at the screening I attended.

Fine; they deserve some beefcake after years of putting up with “Spider-Man’’ and “The Hulk.’’ Hemsworth’s Thor is annoyingly arrogant in the initial scenes, before his one-eyed daddy, Odin (Anthony Hopkins, rumbling discreetly in search of a paycheck), exiles him to Earth for trying to jumpstart a war with the evil Frost Giants. Once he’s humbled (and after some amusing scenes of him bulldozing through small-town diners in search of mead), the star lightens up and is good company for the duration.

A good thing, too, since “Thor’’ is loaded down with sub-Wagnerian huggermugger. The film’s designated menace, the Norse trickster (and Thor’s brother) Loki, is played by the weedy British actor Tim Hiddleston as a passive-aggressive bad guy — it’s a portrait of the super-villain as a young man. Thor also has four knightly sidekicks who are plotting to return him to Asgard, including the Falstaffian Volstagg (Ray Stevenson), the Robin Hoodish Fandral (Josh Dallas), the Amazonian Sif (Jaimie Alexander), and Hogun (Tadanobu Asano of the 2001 cult classic “Ichi the Killer’’), a samurai who appears to have taken a left turn at the Tokugawa Shogunate.

Toss in the Frost King (Colm Feore), Thor’s mum (Rene Russo), and Idris Elba looking like a “Tron’’ extra as the Guardian of the Rainbow Bridge and you’ve got one crowded dance floor in Asgard. Nor is Earth much better, with Stellan Skarsgard as Jane’s scientific mentor (and the only actual Norseman anywhere near this movie), Clark Gregg returning from “Iron Man’’ as the imperturbably bland agent from SHIELD, and a neat little cameo by Jeremy Renner as an operative with serious archery skills. (And there are the Marvel elves again, rolling in another piece of “Avengers’’ furniture.)

Given this rugby scrum, it’s surprising that “Thor’’ moves along at a fairly brisk clip, entertaining us while never getting us to believe any of it matters the least. Also surprising is the director: Kenneth Branagh. But maybe not so surprising, since the actor-director’s experience with Shakespeare allows him to spin this movie’s tin-eared comic-book dialogue with the right amount of ersatz nobility. “Thor’’ shows the Marvel movie formula — amp up the laughs, deploy stars smartly, protect the franchise at all costs — at its most obvious and efficient. It gives mediocre a good name.

Ty Burr can be reached at tburr@globe.com.