Executive Producer: Lori Forte   Director: John C. Donkin   Screenplay: Jim Hecht, Will Schifrin and Ray DeLaurentis   Cast: Utkarsh Ambudkar, Simon Pegg, Justina Machado, Vincent Tong, Aaron Harris, Dominique Jennings, Sean Kenin Elias-Reyes, Jake Green and Skyler Stone   Distributor: Disney+

Grade: C-

The first five installments of the animated “Ice Age” franchise, which has prospered for some two decades, were full-fledged theatrical release with starry voice casts.  This sixth chapter is skipping theatres, taking the streaming route instead.  It also replaces most of the human cast: Ray Romano, Queen Latifah, Denis Leary and Denis Leary, along with several others, are absent, succeeded by imitators, competent enough but largely unknown, and their characters shunted to the sidelines.  The result is less a continuation than spin-off, and the level of imagination, which was already in decline in the last few movies, has plummeted further.

The picture does begin with a prologue involving the hitherto central wooly mammoth couple Manny (previously Romano, now Sean Kenin Elias-Reyes) and Ellie (once Latifah, now Dominique Jennings) and their “family”—Sid the sloth (once Leguizamo, now Jake Green), saber-tooth tiger Diego (previously Leary, now Skyler Stone) and goofy, risk-taking possum brothers Crash (once Seann William Scott, now Vincent Tong) and Eddie (originally Josh Peck, now Aaron Harris).

Crash and Eddie, feeling stifled by their surrogate sister Ellie’s smothering, decide it’s time to go off on their own and eventually find their way into the underground “lost world” familiar from the 2009 picture, “Dawn of the Dinosaurs,” where the beasties live in peaceful harmony with mammals under the watchful eye of Buckminster “Buck” Wild (Simon Pegg, the only returnee in the voice cast), the wild, one-eyed, swashbuckling weasel who was introduced in “Dinosaurs” and brought back in the fifth movie, “Collision Course.”

Unfortunately, the underground world is under threat from Orson (Utkarsh Ambudkar), an ultra-smart little dino with a huge brain who’d been exiled for his Machiavellian ways but has now returned with an army of raptors to establish himself as king and wipe out the mammals.  Crash and Eddie join Buck’s fight against him, though initially they’re often more hindrance than help.  But they learn courage and teamwork from the endeavor, especially after they’re joined in the fray by Buck’s one-time comrade-in-arms (and romantic interest) Zee (Justina Machado), a beautiful striped polecat who balances Buck’s recklessness with strategic planning.

Just about every element of “Buck Wild” is mediocre, from the voice work (Pegg, Tong and Harris are strident and the others pretty bland) and script (the humor is forced, particularly when it aims for juvenile naughtiness) to the animation, which is sometimes jerky and overall lacks the smoothness of the best current computer-generated work—the more apt comparison would be to what one’s likely to encounter on children’s cable channels.  (The job was passed from series creator Blue Sky Studios, shuttered when Twentieth Century Fox merged with Disney, to Bardel Entertainment.) 

Nevertheless young children will probably enjoy the movie’s energy—after all, it’s packed with chases and other action—and vibrant colors, even if the character movement isn’t always crisp and the backgrounds disappointingly flat, without the tactile feel audiences have come to luxuriate in.  There are, happily, pauses in the hectic motion when the narrative periodically shifts to the franchise’s original stars, who track Crash and Eddie in an effort to bring them home and eventually wind up in the underground realm too.  Parents dragooned into watching along with their kids will undoubtedly appreciate them.

Frankly the quality of the “Ice Age” movies was already melting as the franchise wore on—2016’s “Collision Course” was a truly tired take on the giant-asteroid-headed-for-earth cliché—and except technically this addition to the canon isn’t appreciably worse.  But that’s not saying much.  It’s time to move on to a new era.