The first “Secret Life of Pets” was so successful—and, frankly, amusing—that a sequel was inevitable, and here it is. And as usual, it’s not nearly as good.

One can applaud scripter Brian Lynch’s decision to return to what was really the theme of the first picture—the need to adapt to new circumstances—an idea that kids can learn from. Back in 2016, it was the difficulty that Jack Russell terrier Max (then voiced by the now-disgraced Louis C.K.) had in coping with the arrival of a second dog, big, slobbering Duke (Eric Stonestreet), in the household. Now they’re pals, but are confronted with an even bigger challenge—coming to terms with the presence of their owner’s first child, who becomes the center of the family universe.

It doesn’t take long for Max (now voiced by Patton Oswald) to fall in love with little Liam and grow so protective of the tyke that he becomes obsessive to the point of scratching himself to a frenzy. That’s resolved when he and the family take a trip to a relative’s farm, where a gruff old Welsh Sheepdog named Rooster (Harrison Ford, who easily steals the show) teaches him to overcome his fears and face them with the courage of which he’s capable. Lesson learned, by Max and, perhaps, his young audience.

This thread of “Pets 2” has quite a few laughs, courtesy not only of Max and Duke but Rooster and a gaggle of other animals Max encounters there—a goofy cow, a stalker turkey, a naïve lamb called Cotton.

Unhappy, Lynch apparently concluded that there wasn’t enough material in it to serve as the basis for an entire feature—or opportunities for the other characters from the first movie, particularly Kevin Hart’s hyper rabbit Snowball, to get in on the action. So he has turned his screenplay into a sort of animated triptych, with two other story threads added to the mix.

One centers on Snowball, of course, who’s now a happy pet, but still with delusions of grandeur. He dresses up as a superhero and looks for animals to save. Enter Daisy (Tiffany Haddish), a garrulous Shih Tzu. She enlists his help in rescuing a tiger cub called Hu from the cage he’s kept in by vicious circus owner Sergei (Nick Kroll), who wants the beast to perform dangerous tricks. The new duo’s efforts put them in the sights of Sergei’s nasty wolves and sinister monkey, but also draw disabled old basset hound Pops (Dana Carvey) and his brood of pups into the action.

While the frenetic Snowball-Daisy arc rushes on, a third periodically intervenes. It centers on perky Pomeranian Gidget (Jenny Slate), whom Max entrusts with his favorite toy—a squeeze ball called Busy Bee, when he leaves for the farm. Naturally she loses it, and tracks it to the apartment of the local cat lady. In order to infiltrate the place and retrieve it, she has to ask oversized, happily inactive feline Chloe (Lake Bell) to instruct her how to be catlike. Other friends, like pug Mel (Bobby Moynihan), dachshund Buddy (Hannibal Buress) and guinea pig Norman (Chris Renaud) are called on to help, too.

Throughout, the Illumination Studio animation is fine, and the voice work is uniformly excellent (although Hart, as usual, goes way big; by contrast Haddish is more restrained than she is in many of her live-action performances—though to be sure that’s a backhanded compliment). The incessantly busy, jazzy background score by Alexandre Desplat is a positive element as well, adding plenty of aural dash to the visuals.

But the movie suffers from its scattershot approach, jumping from one of the three story threads to another without ever managing to integrate them satisfactorily, though it tries to do so in the end and each has its moments—the Max section the best (a sequence set in the office of a therapist-vet is a gem), with the cat-centered elements of the Gidget segment coming in second and the rambunctious Snowball part bringing up the rear, though it could very well be the one that kids react to most enthusiastically. The closing-credits sequence, which turns to live-action footage reminiscent of “Craziest Pet” TV shows, has the misfortune of ripping one out of the world the movie’s created too abruptly.

“The Secret Lives of Pets 2” isn’t a terrible sequel, but it comes across as one cobbled together from disparate elements rather than a smoothly-fashioned whole. It will probably amuse most people even though it’s a disappointment overall.