Based on the poster showing two cute dogs – a border terrier and a Boston terrier – I had assumed Strays was a (probably lame) kiddie film with a remit to amuse the aforementioned kiddies during the long, long, very long summer holidays, so here’s what I was saying to myself during the opening moments: ‘Christ on a bike, what the hell is this?’ I can now tell you that Strays is vulgar, rude, offensive and disgusting. But the biggest, weirdest shock? At a certain point I realised it was funny, and rather touching, and that I was having fun. In other words, I was pleasantly surprised. Or, given its frequent scatological content, pleasantly surprised, unpleasantly.

The film is directed by Josh Greenbaum and written by Dan Perrault, and our main dog is the border terrier, Reggie (voiced by Will Ferrell, who of course had to be somewhere in the mix). We first meet Reggie running through a field and chasing butterflies while declaring: ‘This is a great day, the greatest day!’ But it turns out that his owner, Doug (Will Forte), is a stoner brute. Reggie doesn’t know that his name is Reggie. He thinks his name is ‘Dumbass Shitbag’ – you see now how this differs from Lady and the Tramp – because that is what Doug always calls him. Doug kicks Reggie and throws cans at him and shuts the door against him. I did not enjoy this part. I don’t want to see dogs treated cruelly. I am still traumatised by Old Yeller 50 years after the fact. But Doug wants rid of Reggie, as we will always call him, so drives him further and further away, throws his ball, drives home without him. Reggie thinks this a game, the best game, and it’s his job to bring the ball back, as he always does.

But then Doug drops him in the midst of a city many miles away where Reggie is at a loss until he meets another bunch of strays: Bug, the Boston terrier (voiced by Jamie Foxx), Maggie, the rough-coated collie (Isla Fisher) and a great dane, Hunter (Randall Park). Hunter is not insignificantly endowed, shall we say, and when complimented happily confides: ‘I like to keep it clean. I lick it a lot.’ These dogs are potty-mouthed and the F-word abounds as they teach Reggie to negotiate the streets and introduce him to their favourite pastimes, like humping garden furniture. Reggie, who is still pure of spirit, insists he isn’t a stray, but when he tells them what he thinks his name is, the others get it. Eventually Reggie gets it too and they plot their revenge: they will find Doug and bite his penis off. There is no gentler way of saying it.

They have their adventures on their way. Some are full-on gross – an escape from the clutches of Animal Control is scatologically full-on – but some are uncommonly smart, such as the scene involving a labrador (‘the Narrator Dog’), and there is also a clever cameo from Dennis Quaid. The dogs are impeccably rendered. Unlike, say, Cocaine Bear, this isn’t pure CGI. Instead, it’s a complicated mix of real dogs and special effects and the results are stunning. All the strays have a backstory and the film understands the nature of dogs much better than, for example, Wes Anderson’s Isle of Dogs. It is funny, I think, because it finds some kind of balance between its wild excesses and saying something true about man’s best friend. Will Reggie bite Doug’s penis off? Or, when it comes to it, does he just want Doug to call him ‘a good boy’? I welled up at the end. You may like it. Just don’t take the kids.