"“Some of the sequences may go down like a lead balloon, but every unfunny moment is contracted with something hilarious...”"

When watching either the Jackass TV show, or one of their three cinematic endeavours, the Grandpa character, played by Johnny Knoxville, was never a particular highlight as such, seemingly without the depth nor comic potential to then be realised in a spin-off feature length film. However by remaining faithful to the Jackass brand, while sticking (somewhat loosely) to a narrative, it seems any initial trepidation has been swiftly displaced, as Jeff Tremaine's Bad Grandpa is really damn funny.

When 8-year-old Billy (Jackson Nicoll) is left without a home – after his mother is sent to prison – he is left in the hands of his recently widowed grandfather, Irving Zisman (Knoxville) – as the pair set off on a road trip across America (with Irving's deceased wife in the boot), to reunite Billy with his father, who has his eyes solely on the child benefits cheques. Though originally Irving wants nothing more than to drop Billy off and go and spend his money on strippers ans alcohol – the pair strike up the unlikeliest of bonds, as soon the idea of being apart fills neither with any joy.

Though completely inane, vacuous, offensive and illusory – that is by no means a bad thing (bear with me). Sometimes you don't need much intelligence or wit, and the occasional fart gag – or in this instance, following through all over the wall of a restaurant – is exactly what you hope for, and expect from such a film. As far as candid camera films go, this hasn't got quite the same intelligence or political satire that Sacha Baron Cohen's Borat or Bruno had in abundance, but it's not really trying to be that kind of movie. Nonetheless, some of the reactions are just priceless – and keep an eye out for one of the greatest double takes in the history of cinema (again, in the poo on the wall scene).

The slapstick humour is hilarious in parts though, and lovingly predictable. You see Irving and Billy walk into a wedding reception and instantly, in the background, you can make out the silouhette of a lot of champagne glasses balancing on top of each other. You know that eventually they're all going to end up on the floor, with Knoxville lying hopelessly beneath them. Lo and behold, that's exactly what happens – but it's what you wanted to happen. This picture doesn't disappoint in that regard. The highlight of the piece, however, is the sharp and brilliantly satirical scene at a beauty pageant. It's the only real scene that displays Knoxville's ability to cleverly put the dagger in some of America's most questionable of traditions, and to show it off as the absurd, unethical event it truly is.

Knoxville also squeezes out many endearing qualities from the public too, exploiting the good nature of many strangers, who are so caring and concerned about Billy's well-being. It's a great performance by Nicoll too, he has a real sincerity to him, but executes it in such a deadpan manner. The relationship between Billy and his grandpa is somewhat heartwarming at times, though writers Knoxville and Tremaine – alongside Fax Bahr, Spike Jonze and Adam Small – do struggle to tie the various escapades and stunts in with the narrative at hand. They have kept this film open – by making it a mere road trip movie – but sometimes the way the characters gravitate towards certain places and jokes, is done so with a degree of contrivance.

Not all of the jokes work – as this film certainly has its moments, both good and bad. Some of the sequences may go down like a lead balloon, but every unfunny moment is contracted with something hilarious. When Bad Grandpa misses – it misses by a mile. But when it hits, it can be a joy to behold.