LOS ANGELES - Increasingly, studios are slapping 3D on movies not to add entertainment value but to conceal a lack of dimension in a movie's story or characters. While not the worst in recent 3D films, "Gulliver's Travels" is more gimmicky than a crackling good yarn.

The film feels rushed and slight at every point. Thanks to inspired clowning by Jack Black and a solid cast that breathes life into an inert story, the movie works as a moderately entertaining children's movie. Opening domestically on Christmas Day via Fox, "Gulliver's Travels" should enjoy a brief burst of box-office activity.

The great irony about Jonathan Swift's 1726 novel, "Gulliver's Travels," is that librarians and schoolteachers have forever relegated to the shelves of children's books what is, in fact, a scathing moral satire of the corrupt English society of his time and mankind's proclivity for irrationality and vice over common sense and virtue. (Mark Twain's equally satiric, "The Adventures of Huckleberry Finn," suffers a similar fate.) There is something about the comical idea of a normal-sized human striding through a kingdom of tiny people -- an image derived entirely from Gulliver's first voyage to Lilliput -- that consigns his literary masterpiece to the world of elves, trolls and fairy princesses.

The latest version, which comes from several filmmakers with backgrounds in animation, casts Black as a shy, ambition-challenged mailroom clerk for a New York newspaper. This opening setting is a nostalgic one, mind you, as its busy newsroom is crowded with employed journalists, and a travel editor occupies an office fit for a managing editor.

Black's Gulliver has a long-standing crush on that travel editor (Amanda Peet) but can never bring himself to ask her out. Goaded by a colleague into approaching her, he winds up not with a date but with a travel assignment.

That takes him to the Bermuda Triangle, where a storm washes him into an inter-dimensional portal that carries him to Lilliput, where remnants of Swift's tale take over. The kingdom is made to look somewhat like 18th century England and features mostly British actors.

The tiny Lilliputians struggle to imprison this "giant," but when he escapes, he performs heroic deeds that save the people. Among these displays of bravery, one actually borrowed from the original story, is the day when he puts out a fire in the royal palace by urinating on the flames.

Emboldened by his newly acquired size, Gulliver now exaggerates his past, drawing on film culture to cast himself as the victorious hero of stories ranging from Star Wars to Titanic. This kernel of an idea -- a small man suddenly talking big -- never develops beyond a few gags involving contemporary movies, however. In the tiresome manner of most studio-generated comedies, its protagonist must undergo a trajectory that confronts him with his character flaws and improves his defective personality.

Gulliver also inserts himself into a romantic triangle featuring the island's princess (Emily Blunt), her military suitor (Chris O'Dowd) and the commoner (Jason Segel) who really loves her. Here again a conspicuous lack of imagination finds director Rob Letterman ("Shark Tale," "Monsters vs. Aliens") and writers Joe Stillman ("Shrek," "Shrek 2") and Nicholas Stoller ("Forgetting Sarah Marshall") pillaging ideas from Cyrano de Bergerac to "Transformers," "Iron Man" and even Black's "School of Rock."

When Peet's character somehow turns up in Lilliput -- that's one busy inter-dimensional portal -- the movie truly loses its mooring. There is even a sequence, borrowing loosely from Gulliver's second voyage to Brobdingnag, where Black, a tiny friend and a giant child all occupy the same frame in a CGI shootout. Any sense of fun slowly drains away as the movie insists on highlighting effects over character and story.

Black does his best to keep you entertained, and the rest of the cast, which includes a dignified Billy Connolly and an aloof Catherine Tate as Lilliput's king and queen, keep tongues firmly planted in cheeks as they maneuver around the CG effects. Blunt amusingly spoofs some of her serious films, such as "The Young Victoria," while O'Dowd and Segel achieve a farcical rivalry.

The production is smooth given how it's pieced together from so many elements. But there is something cheesy about the overlit kingdom of six-inch humans and the way Black prances around with no thought for the countless creatures he must be trampling to death.