‘Tully’: Funny moments, surprise twists as a nanny eases a mom’s baby blues

Jason Reitman and Diablo Cody are three for three.

In 2007, director Reitman and screenwriter teamed up for “Juno,” the whip-smart teen pregnancy comedy for which Cody won the Oscar for original screenplay.

Four years later, Reitman and Cody gave us the wickedly funny “Young Adult,” with Charlize Theron as a screwed-up writer who returns to her hometown on an ill-conceived mission that blows up in spectacular fashion.

Now comes “Tully,” which reunites Reitman, Cody and Theron in a crackling good domestic comedy/drama with smart, economic, often hilariously spot-on dialogue, expertly crafted performances from the cast — and some strange and unexpected detours that might give you a case of plot whiplash when you realize exactly what’s been going on.

For the role of Marlo, a harried mother in her early 40s who doesn’t have time to brush her hair, Theron reportedly packed on some 50 pounds and “let herself go,” as we like to say about beautiful actors who undergo such transformations for roles — but even as Marlo lugs herself around and laments how men don’t look at her the way they once did, she still looks like Charlize Theron.

It’s the performance that matters, and Theron delivers some of her best work as the sarcastic, moody and sometimes downright bitchy Marlo, who always seems on the verge of losing it even as it’s clear she still dearly loves her husband Drew (a low-key and terrific Ron Livingston) and her three children: 8-year-old Sarah (Lia Frankland); 5-year-old Jonah (Asher Miles Fallica), a special-needs child prone to intense meltdowns over the slightest hiccup to his day, and a newborn daughter, Mia, who is keeping her up all night.

Marlo’s casually insufferable and quite rich brother Craig (Mark Duplass) and his perfect and perfectly annoying wife Elyse (Elaine Tan) offer to pay for a “night nanny,” who will come to the house every night and look after the baby so Marlo can get some rest.

It’s actually a generous offer, but Drew points out Craig will lord it over them forever, and Marlo worries it will seem as if she’s passing off mothering duties to a stranger.

An intense and funny montage set to a percussion beat shows Marlo going through a seemingly endless routine of caring for her family, bringing home just how exhausting life has become for her — and making us understand and applaud when she decides that whole night-nanny thing is worth a try.

Enter Tully (Mackenzie Davis), who is 26 and in a state of perpetual wonder at the awesomeness of the world. Tully is a trippy hippie type who can almost overwhelm you with the sheer force of her New Age energy and personality. She’s also an amazingly efficient godsend who instantly bonds with the baby and also finds time to clean the house, bake cupcakes, become a sounding board for Marlo and generally restore relative tranquility and stability to the household.

“It’s like I can see color again,” enthuses Marlo as she marvels at how wonderful life can be when one doesn’t feel like a walking zombie.

Director Reitman keeps things moving along at a brisk pace, and Diablo’s screenplay is brimming with clever but authentic-sounding dialogue. This is a movie filled with neat touches, from Elyse having a tiny dog named Prosecco to a talent pageant in which a girl’s talent is “Pilates” to Drew climbing into bed each night and immediately putting on a headset and reaching for the controls so he can retreat into a violent video game to a stranger in a coffee shop lecturing the pregnant Marlo about drinking even decaf, because there are trace elements of caffeine even in decaf.

The final chapters of “Tully” take us to a place I certainly didn’t anticipate, causing us to re-examine everything we’ve seen from the outset. It might not be a perfectly constructed journey, but it’s pretty close.

★★★1⁄2

Focus Features presents a film directed by Jason Reitman and written by Diablo Cody. Rated R (for language and some sexuality/nudity). Running time: 94 minutes. Opens Friday at local theaters.