PET owners like to believe they know what darling Rex and Tiddles get up to when they're not around – but Hollywood's about to remind us of the real truth.

Nine years ago, the live action film Cats & Dogs hit our screens. It starred animals rather than humans, and pet lovers learned that their furry friends were really super-spies whose underground headquarters harboured more gadgets and gizmos than a Bond lair.

The film's sequel, Cats & Dogs: The Revenge Of Kitty Galore, takes a slightly different tack. Instead of fighting against one another, the ever-warring cats and dogs are forced to "paws" for thought, put their differences aside and team up in order to save the day, as an embittered former agent of spy organisation MEOWS tries to take over the world.

The hairless Sphynx cat Kitty, voiced by Bette Midler, provides just one of the recognisable voices in a cast which includes Nick Nolte, Chris O'Donnell, Christina Applegate and Roger Moore – who plays tux-wearing chief of the MEOWS spy agency, Tab Lazenby.

Applegate, who recently announced she's pregnant with her first child, says she had another reason for making the film. "I wanted to have a legacy of movies that my kids could see, because there's nothing that anyone under the age of 18 could watch," says the 38-year-old, who recently beat breast cancer.

"It's nice to have these movies like the Chipmunks and this to show my kids, so they can see their mum did something kinda cool."

Beaches actress Midler, 64, also admits she wanted a role in a family-friendly movie.

"I wanted to make something a little bit wholesome, not too strenuous, full of laughs and fun. This, I think, is the best example of it. It's got something for everybody and it's really well done. I don't know how they did it."

She's not joking. As one of the voice cast, Midler simply recorded her role in a sound studio, while the real acting was left to the trained animal cast, often rescue cats and dogs.

"I didn't see anybody else but the director, the producer and the sound people. It was intense," reveals Midler. "You go in there, watch it as a sketch and then they take it away and animate it – I had never seen anything like this. I was shocked, I didn't know how things had come this far."

And things have come even further since 2001. Many of the animals' stunts are aided by elaborate computer-generated imagery (CGI), one of the cast is purely animatronic, and there is a 3D dimension.

Applegate describes how, in Cats & Dogs world, the pets have elaborate secret lives: they wear clothes, have their own vending machines and travel by jet pack and rocket car.

"It's absolutely absurd and fantastic, this whole secret hi-tech world they have and yet it's presented as perfectly normal," says Applegate. "It's as if all that other stuff they do – like purring and doing tricks – is just designed to distract us from what's really going on."

And what is really going? Well, the first film saw the two rival pets in a ferocious furry battle for dominance – the cats unleashing their highly-trained ninja assassins in a desperate attempt to supplant dogs' hallowed spot as "man's best friend".

This time round, the rival DOG and MEOWS agencies come together to foil Kitty Galore – a rogue bald cat who lost all her fur when she fell into a vat of depilatory cream, while trying to escape guard dogs at a cosmetics lab. Shunned by her human family, she takes to the streets and is adopted by a magician who dresses her up in a ridiculous array of outfits.

"I don't think Kitty is misunderstood, she's just evil," says Midler, laughing. "I like her a lot though. Villains are the most fun to play – they're so over-the-top and usually the silliest. Here you have a wonderful combination of evil and absolute ridiculousness, which is irresistible."

Cats & Dogs: The Revenge of Kitty Galore is released in cinemas on Wednesday