One of the many bright spots in Judd Apatow's much-loved dramedy Knocked Up was the hilariously acrimonious married couple Pete and Debbie, a pair of side characters memorably played by Paul Rudd and Leslie Mann. Here Apatow gives them their own film, This Is 40, an uproariously funny and rousing drama about the pangs of middle age which avoids the slightly forced revelatory quality of the original film, instead opting for a more convincing and relatable bout of pragmatism. At the end of the day, this is a film about what really matters in life - family. The film begins with Debbie's 40th birthday - despite her protestations that she's 38, or maybe 37 - while Pete's is only a few days away itself. They're clearly shocked at the prospect of becoming even remotely "old", that's only the first of the issues in a story that ably divorces itself from simply becoming another "white rich people problems" film. Pete now runs a record label, but is struggling to make ends meet, and needs to scout a hot band soon or risk going bust, while Debbie's boutique store has a $12,000 defecit, which one of her employees (Megan Fox and Charlene Yi) might be responsible for. Add to this the fact that Pete is secretly loaning boatloads of money to his financially unstable father, Larry (Albert Brooks), and it's evident something has to change. Even before their financial situation begins to overwhelm, though, it is clear that comfortable complacency can itself be a problem, and these added woes only further put their relationship to the test. Perhaps the most tellingly provocative moment comes when Debbie asks Pete, "If I hadn't gotten pregnant twelve years ago, would we even still be together?". It's a taxing question, and one likely to reverberate through the minds of many married couples sat watching the film. Piling up the problems as he does, Apatow nevertheless manages to turn potentially miserable material into something uplifting and resonant, with his unmistakable blend of brutal honesty and universal emotion. Clearly a personal work for Apatow though one he insists is not autobiographical, he manages to make the drama funny in a serious way, if that makes sense. The film's bent of stinging humour largely stems from how brutally honest it is with regards to relationship dynamics and the less-flattering aspects of the ageing process. Credit to Apatow for shrewdly casting his entire immediate family as three of the leads (Mann being his real-life wife, playing alongside their two daughters); their real-life familiarity is apparent on-screen and enhances our engagement, aided entirely, of course, by the fact that Apatow's daughters, Maude and Iris, are fantastically talented young actresses in their own rights. The writer-director's casting never feels like an act of nepotism; rather, it a decision built into the fabric of the story, while Paul Rudd, as likeable a lead as he has ever been, slots firmly into the family dynamic. In fact, casting from top to bottom is absolutely faultless; Brooks is back to playful form - a pleasant tonic after his fantastically vicious work on Drive - as Pete's father, though underscored by a certain sadness at his financial woes and the exhausting presence of his new family, complete with a gang of young triplets. Getting a trickier engagement is John Lithgow, playing Debbie's father Oliver, a wealthy plastic surgeon who scarcely connects with his daughter, but to her deep, incredulous distress, has made a second family with whom he appears to have a deep, emotional bond. Admirably, Apatow doesn't resolve either of these threads with a quick fix; everything is about baby steps, and as the film makes clear, sometimes accepting that the edges are always going to be a little rough. Rounding out the cast, Lena Dunham, Chris O'Dowd, Melissa McCarthy, Charlyne Yi and Jason Segel all get great cameos, but perhaps the most memorable comes from Megan Fox, who delivers what is easily her best performance to date as a sexy employee working at Debbie's store. Given that a 135-minute runtime is a risky prospect for a comedy whether dramatic in nature or not, Apatow pulls it off with stunning aplomb, maintaining a laugh-a-minute gag-rate that is certainly not to be sniffed at; in fact, it might just be the best value for money laugh riot to come down the pipe in some time. As he does so well, Apatow melds crude dick jokes with resolutely honest observational comedy, such that the film is likely to be a hit with the Knocked Up crowd; that is, people who were young adults themselves when that film was released, and who are now settling down with families. Better than most other filmmakers, Apatow also manages to slyly massage in some pop-culture references - namely a running gag about the eldest daughter's obsession with Lost - that remarkably don't feel forced, and actually have something of a point beyond making us laugh. This relentlessly hilarious and quietly moving riff on middle-aged growing pains stands as a rare spin-off that outdoes the material it spawned from, and is Judd Apatow's best feature to date. This Is 40 is in US cinemas December 21st and in the UK on February 14th, 2013.