One realizes that the level of invention in the “Ice Age” franchise has slowed to a trickle very early on, when the first big gags in “Collision Course,” the fifth installment, revolve around: (1) wooly mammoth Manny (voiced by Ray Romano) forgetting his wedding anniversary and annoying his wife Ellie (Queen Latifah) in the process, and (2) Manny kvetching about the engagement of his daughter Peaches (Keke Palmer) to Julian (Adam Devine), a happy-go-lucky doofus who rubs his prospective father-in-law the wrong way. That immediately puts it into a category with mediocre TV sitcoms of the 1950s, and the succeeding sequences in the episodic family film aren’t much more imaginative. Crammed with characters that grow increasingly irritating as it ambles on—even the usually reliable laugh-getting squirrel Scrat wears out his welcome over the course of the movie—“Collision Course” proves a pretty tedious slog.

Rather than just appearing as an incidental figure in self-contained material, it should be noted, Scrat is an integral, if isolated, character this time around. In pursuing the usual acorn, he—or is it she?—stumbles into a marooned space ship that he accidentally charges back into operation and is whooshed off into space on. In finagling with the controls, he causes all sorts of trouble, and one result is that a huge asteroid is sent on the titular collision course toward earth—threatening a catastrophe that will end mammal life on the planet just as an earlier one had wiped out the dinosaurs. Shades of “Armageddon” and “Deep Impact”!

Enter Buck (Simon Pegg), the one-eyed weasel from installment three, who arrives in Manny’s world pursued by three angry Dromaeosaurs—nasty Gavin (Nick Offerman), his oversized daughter Gertie (Stephanie Beatriz) and his nebbishy son Roger (Max Greenfield). Buck explains that to avoid destruction, he, Manny and all the others must proceed to the site where such asteroids had previously struck earth and try to prevent this one from following their example.

That starts the “trek” part of the picture, in which Manny, Ellie, Peaches and Julian are joined by the familiar gang—lovesick sloth Sid (John Leguizamo), saber-toothed tigers Diego (Denis Leary) and his wife Shira (Jennifer Lopez), bickering opossums Crash and Eddie (Seann William Scott and Josh Peck), and Sid’s cranky Granny (Wanda Sykes). After a series of adventures they come to their destination, where New Agey Shangri Llama (Jesse Tyler Ferguson) presides over a paradise of endless youth called Geotopia that also houses Brooke (Jessie J), who becomes a prospective mate for Sid, and Teddy (Michael Strahan), a rabbit who’s drawn to Granny. Unhappily, the special properties of Geotopia are dependent on magnetic bits of earlier asteroids that, Buck determines, must be collected and launched into space to divert the destructive behemoth headed earth’s way. Doing that will force the Geotopians to give up their youth and require convincing the Dromaeosaurs to cooperate in the effort—as well as preparing a volcano to serve as a launching pad.

All of that makes for a busy but strangely flat animation extravaganza that feels tired despite its frenetic effort to entertain. The script feeds characters plenty of lines, but few evince the slightest shred of wit, and the multiplicity of characters leave some of the older ones, like Leary’s and Lopez’s tigers and Queen Latifah’s Ellie, almost nothing to contribute, while others, like Leguizamo’s Sid, Wanda’s Granny and Scott and Peck’s opossums, get entirely too much screen time. Even Manny fades into the background, not just because of Romano’s laid-back delivery but because Pegg’s hyperactive Buck virtually takes over the movie. Introduced inexplicably with a laugh-free version of Figaro’s “Largo al factotum” from “The Barber of Seville” (put to far better use by Looney Tunes decades ago), the motor-mouthed Brit quickly becomes an exhausting bore, though a couple of sequences in which he morphs into Neil deBuck Weasel (voiced by Neil deGrasse Tyson) to explain loony scientific arcana are amusing.

The new characters also fail to click—not only the trio of Dromaeosaurs but Ferguson’s Shangri Llama, the punning name a bad enough idea, but the characterization—a spacey, blissfully euphoric goofball—an even worse one. By the time the crew celebrate the rescue of the planet, you’ll probably be ready to celebrate as well—the end of the movie. Even the epilogue in which Scrat lands on Mars is unlikely to lift your spirits.

Recent animated successes like “Inside/Out,” “Zootopia,” “Finding Dory” and “The Secret Lives of Pets” have really raised the bar for this sort of fare. By their standards, “Collision Course” comes off as a serving of stale leftovers.