The Secret Life of Pets 2 is a so-so animated follow-up

Artistically, there wasn't any great reason for it, but since the first movie, from 2016 cost about $US75 million ($A109 million) and grossed more than $A1.2 billion (figures from Box Office Mojo) and in Hollywood, money always talks loudest (there's even another Toy Story sequel, though the original trilogy ended on a perfect note). If it worked once, surely it will work again? That's the theory.

That said, Pets 2 is a pleasant enough diversion, mediocre with some nice moments. It's something lively for the kids that's painless enough for the adults, too, but it's nothing memorable. One of the film's problems is the multiple storylines it juggles seem rather tenuously connected, so it feels like a few short films rather clumsily brought together at the end.

The opening is reminiscent of the Disney classic Lady and the Tramp (a film with much more emotional impact, if less emphasis on comedy).

Neurotic terrier Max (voiced by Patton Oswald, replacing the disgraced Louis CK) feeling a little displaced when his owner, Katie, marries and has a son, named Liam, Curiously, the other dog, Duke - voiced by Eric Stonestreet - doesn't seem to have any problem with the new arrival - in fact he doesn't have all that much to do, a casualty of the film's large cast and multiple storylines.

Max soon warms to Liam, however, and feels protective towards him. So much so, he develops an anxiety-based itch and is fitted with a dog cone.

The family, including the dogs, goes to a relative's farm where the dogs, especially Max, experience culture shock. Max comes under the tutelage of gruff sheepdog Rooster (Harrison Ford - a casting coup - who sounding reminiscent of both John Wayne and Clint Eastwood) who works to toughen him up a bit.

Meanwhile, Max has entrusted his favourite toy, Busy Bee, to his girlfriend (dogfriend?) Gidget (Jenny Slate) but it ends up in the apartment of an old woman and her many cats (this is a pretty ailurophobic movie). Gidget, with the help of tabby Chloe (Lake Bell), disguises herself as a feline to try to retrieve it.

And white rabbit Snowball (Kevin Hart) assumes his superhero persona, Captain Snowball, to help dog Daisy (Tiffany Haddish) rescue a white tiger, Hu, from the cruel Russian circus owner Sergei (Nick Kroll with stereotypical evil Russian accent).

It all feels like a bunch of ideas tossed together for the heck of it, with a few good gags an air of amiability but nothing to stick in the mind after exiting the cinema.

The sequel's budget is about $A116 million and its gross at the time of writing, a couple of weeks after release, was about $238 million: disappointing to those who watch these things expecting instant megagrosses.

If the film keeps bringing in the money to make a healthy profit (apparently movies need to gross two, or possibly three, times their budget to break even) we can probably expect to find out more about the menagerie in three years or so (though it really isn't necessary).

Otherwise, the makers might have to come up with a new idea.