Parenting is perpetual sacrifice. Or so says Jason Reitman and Diablo Cody, the directing-writing duo behind poppy cult classic Juno, with their comeback collaboration Tully. A dramatic comedy or comedic drama, depending on how you want to look at it, Tully is a soaring success no matter what box you want to put it in; a well-meaning, deeply felt, irreverently mature exploration of growing pains and adulating. Charlize Theron is a knock-one in this deliriously enjoyable feature that has no short supply of wit, bite and verve with a shot of mindfuck mixed in to boot.

Reitman has been stuck in a rut since his last project with Theron (Young Adult) but has demonstrably moved past a mid-life directing crisis, hurdling the ennui of Men, Women and Children’s cheap ensemble posturing and the cheesy schmaltz of Labor Day’s fetid forbidden love story. With Tully, Reitman returns to the intersection of sarcasm and sincerity with a film that is heartfelt, pointed, poignant and often contagiously hysterical.

Sharp-tongued and unexpectedly trippy, Tully tells the story of Marlo, played by an award-worthy Charlize Theron, a free-spirit trapped in suburban tedium, trying – and failing – to keep up with the demands of her family. Her well-meaning but doofy husband Drew (Ron Livingston) helps the kids with their homework and labors to pack their lunches but their relationship is one of cool detachment, the few moments they have to themselves filled with iPad adult reality shows and headphoned Gear of Wars 3 gaming. Always separately.

With the arrival of a new baby, Marlo’s yuppie brother Craig (a douchetastic Mark Duplass) and his obnoxiously pilates-sculpted wife Elyse (Elaine Tan) offer the bizarre gift of a night nanny. Basically, a trained professional who comes to your house at night to take care of your newborn while the new mother gets some much-needed rest. Her name is Tully (Mackenzie Davis). And she’s a punk-rock angel of sorts.

In its humble 96 minutes, Tully manages more than most films that linger over two hours, economically measuring in levity and dramatic gravitas, genuine pathos, and well-earned giggles. Scenes are often hilarious and heartbreaking, like when Marlo defeatedly removes her tattered blouse at the kitchen table, soiled by spilled milk, and her children stare at her bulging gut in horror and beg, “Mommy, what’s wrong with your… body?” Cody lines the script with moments like this, layering cringe comedy in with the feels.

In addition to its rich script – which is full of eyebrow-raising twists and turns – one of Tully’s greatest assets is its stars. Charlize Theron gives a star-affirming performance as Marlo, a flustered mother of three, battling sleep deprivation, trying to fulfill the gleeful role of mother and wife but running definitively on empty. Theron gained a mighty 50 pounds to play the paunchy matriarch (her key was a constant barrage of potato chips) and the physical transformation informs the dimming internal light behind her baggy eyes. This is a wonderfully subtle performance, decorated with palpable exhaustion, littered with red herons of postpartum, and it’s a testament to Theron’s transformative power as a performer.

And no matter how good Theron is – and it’s worth repeating, she’s fantastic – Mackenzie Davis almost steals the show as the titular Tully. From the moment she shows up on Marlo’s doorstep, Davis’ creation is magnetic. She’s like a hipster Mary Poppins and Davis lets her spirited earnestness boil from every pore. With her wide-eyed, world-is-my-oyster approach to life, Tully sees a tapestry of possibility everywhere she looks and her unpolished positivity and chic enthusiasm are infectious, reigniting Marlo’s fuse, sparking a zeal for actual living, sharpening qualities lost but not forgotten. The chemistry shared between the actresses is fire as the tight-knit bond of their characters grows in unpredictable fashion.

A few complaints that lodged with me – the camerawork itself sometimes seemed a bit misplaced, as if the framing was perpetually a foot lower than it ought to be, cutting off the tops of characters heads to favor their midsections and knees. I wondered if it were a directorial choice but after wracking my brain for why such a decision would be made, still come up dry.

What got under my skin even more was the fact that Marlo’s middle child, Jonah (Asher Miles Fallica), suffers many symptoms of autism spectrum disorder (aversion to loud noises, inexplicable pattern-driven preferences, low social awareness but high intellectual capacity, etc.) but is constantly referred to as “quirky” (a term once often prescribed to those afflicted by generations not as educated about the disorder.) And yet the A-word is never mentioned, an uncomfortable diatribe about his being “retarded” adding to the discomfort and sticking out like a sore thumb in an otherwise “woke” script.

These few quibbles aside, Tully is a soaring success that rightfully deserves adoration. And though I’m often reticent to watch movies more than once or twice, Tully is the kind of cinematic treat – a cult classic well in the making – that you’ll want to rewatch again the second it’s over, not just to help piece together various narrative clues but to revisit the rib-tickling jokes and hang out with these characters for a little longer. If Tully is the conclusion of one Reitman-Cody trilogy then I hope it’s the start of another, the pair’s professional marriage aging like a fine wine and developing some mystique, novel, deeply compelling format.

CONCLUSION: Jason Reitman and Diablo Cody have made a monstrously chewy feature film with ‘Tully’, a film brimming with wit, humanity, and imagination. Stars Charlize Theron and Mackenzie Davis have rarely been better in this hysterical examination of familial stressors that feels a bit like ‘Mary Poppins’ and ‘Fight Club’ collided.