How nice is too nice? How sunny too sunny? Just how much Technicolor optimism can one working class corner of London bear before thoroughly breaking down the purveyor of this bubbly outlook with the grim scowl of reality? These are the questions posed in Mike Leigh's Happy-Go-Lucky. And Leigh knows a thing or two about those grim realities. He's spent much of his career exploring just how they rip us apart.

Sally Hawkins stars as Poppy, a 30-year-old London primary school teacher with a smile and a joke always at the ready, whether for the dour-faced commuters on the bus or her sour-tempered driving instructor. Her disposition is so relentlessly cheery that even when she locks up her back during her weekly trampoline class (Leigh uses shots of Poppy endlessly bouncing to great metaphorical effect), her response to the intense pain is to giggle even as she winces. Poppy is on one candy-colored ride of a life, and wants to bring everyone along with her, cheering up the surly bookshop clerk, getting to the bottom of why one of her young students is acting out violently, even reaching out to a homeless man of marginal sanity in a dark and deserted construction site.

With this last case especially, Poppy's mission to brighten the corners of the world seems to be almost reckless, and one spends much of the film waiting for the other shoe to drop. Her near constant smile might border on Pollyannaish, and the whole thing could have easily come over as a saccharine bit of look-at-the-bright-side affirmation. But Leigh isn't interested in that. He challenges Poppy's happiness in very real, and very profound ways, and if you leave the theater feeling uplifted (and unless your heart is made of cold gray concrete, you will), it wasn't due to manipulation, but really a result of Leigh and Poppy having honestly earned it.

Two previous film characters spring to mind while watching Happy-Go-Lucky, both of whom serve as counterpoints to Poppy. One is Amelie, Jean-Pierre Jeunet's delightful Parisian do-gooder from the eponymous film. Leigh's film may lack the fanciful visual flair of Jeunet's, but that's mostly because, like all of Leigh's film's, he's firmly grounded in the real world. Jeunet edges into fantasy, much to Amelie's benefit, but Leigh makes his work tougher by making Poppy face up to a world that seems determined to bring her down, and in all-too-familiar ways. It's a world in which Leigh's work is often entrenched, particularly in Naked, which is Happy-Go-Lucky's other reference point. That film's protagonist, Johnny, is a wickedly smart drifter who experiences a profound sense of disappointment in nearly every human he meets, and works overtime to distance himself from humanity as a result. Poppy is Johnny's flipside, taking every sling and arrow and transforming it into a rather refreshing (but never too sweet) glass of lemonade, always trying to draw the rest of the world into her orbit.

What the film also shares with Naked is a status as an immediate masterpiece. It's so rare that such a happy and funny film rings so true, and it owes a great deal to Leigh's singular filmmaking style, which famously involves developing the script out of improvisations with his actors. Hawkins gives a performance that should be a no-brainer for an Academy Award (or at least a BAFTA, if Americans end up ignoring the film), and the lived-in feel of the film is established as soon as she appears on screen, less a character than a fully-formed human being. Those moments when life begins to overwhelm, when Hawkins turns down Poppy's smile and her eyes turn reflective, bring a depth to the character beyond just what's in Leigh's script and staging. The supporting cast of her friends and co-workers are just as well drawn, and other characters, her flamenco and driving instructors particularly, manage to be both hilarious and tragic. You know, just like real people.

Happy-Go-Lucky is now playing at Landmark's Bethesda Row Cinema.