PIRATES OF THE CARIBBEAN: AT WORLD’S END (2007) - Pass

ARCTIC TALE (2007) - Pick

FORD AT FOX: THE COLLECTION (2007) - Pick

New this week on DVD, Pirates of the Caribbean: At World’s End swells the ranks of franchise threequels foundering on the rocks. In every respect it outdoes its predecessors — except in charm, entertainment and fun.

Johnny Depp still reels and prances as Jack Sparrow, but the character’s appeal was always that he was as much con artist as pirate, with a blend of quirky brilliance, hot air and self-aggrandizement.

All that is gone here. Though back from Davy Jones’ Locker, Jack’s a shadow of his former self, a dazed and confused prisoner of a plot he understands no better than we.

If Jack was the series’ Han Solo figure, Will (Orlando Bloom) and Elizabeth (Kiera Knightley) were the Luke and Leia — the lowly but valiant young hero, the feisty action princess. Now they’re more like the Anakin and Amidala, with too much angst and self-seriousness, and no time amid plot machinations for the lighthearted chemistry of the earlier films. So much promise unfulfilled, so many setups leading only to letdowns.

At World’s End vastly expands the scope of the Pirates of the Caribbean universe — a summary would be a futile gesture — but the mythology now dominates and overshadows the characters and the story, instead of providing the context for them. It’s like what happened in the Star Wars prequels and the Matrix sequels: Over time, franchises tend to become mythology-bound. Too bad.

Also new this week, Arctic Tale is co-presented by the distributors of March of the Penguins and An Inconvenient Truth, and when it grows up Arctic Tale would like to be both of those films. Queen Latifah’s folksy voiceover narration is meant to recall the kid-friendly March of the Penguins, but the overriding theme of climate change does Al Gore proud. (Literally. His daughter Kristin helped write the screenplay.)

Arctic Tale looks like a documentary, but it’s actually a work of fiction — a made-up narrative fabricated in the editing room, with bits of documentary footage shot over several years dovetailed to create an illusory continuity. The breezy tone recalls a 1950s Disney wildlife adventure, but the raw materials are the best thing about Arctic Tale, and the reason to see it.

The filmmakers take us inside the polar bears’ birthing den and beneath ice floes with walruses, spotlighting belugas, humpbacks and, most stunningly, narwhals, so strange they look as if they can’t possibly exist.

As Arctic Tale continues, the global-warming theme grows, until the film becomes an out-and-out infomercial for saving polar bears by turning off your lights and driving a fuel-efficient car. No exaggeration.

Still, I’m glad I saw Arctic Tale once for the spectacular photography, even if it isn’t a movie I would watch repeatedly, with its heavy-handed ideology and overly cute storytelling. It reminds me why many of my favorite nature documentaries — Atlantis, Microcosmos, Winged Migration, Deep Blue — are generally wordless. Sometimes, the less said, the better.

Also notable this week is the Ford at Fox Collection, a gigantic 21-disc box set of John Ford classics. The price tag (over $200!) is beyond most budgets, but many titles, including What Price Glory, My Darling Clementine, How Green Was My Valley and Young Mr. Lincoln, are available individually.

Pirates of the Caribbean: At World’s End: Much swashbuckling violence, mass hangings including a child, gross-out imagery and humor, mild sensuality and innuendo, a soothsayer/witch and a pagan sea goddess. Teens and up. Arctic Tale: Some predatory menace and grisly scenes of predation, some flatulence humor. Fine family viewing. Ford at Fox films: Mostly teens and up.