‘So Help Me Todd’ star on TV’s quirkiest mother/son combo

The spunky banter between “So Help Me Todd” stars Marcia Gay Harden and Sklyar Astin — by turns funny, offbeat and all-too-human — has driven the CBS dramedy to a breakout inaugural season … and an early Season 2 renewal.

The series returns March 2 (9 p.m.) with new episodes after a two-week hiatus. It centers on the mother-and-son dynamic between high-powered attorney Margaret Wright (Harden) and her ingratiating son, Todd (Astin), a talented, quirky, somewhat reckless private investigator who, after losing his license, is hired by his mom to snoop around for information that will help her clients.

Their snappy repartee has been a hit with viewers and critics alike as Todd and Margaret balance their personal and professional lives: Margaret’s second husband left her in the series opener and she juggles different relationships with each of her three children; Todd lives in his married sister Allison’s (Madeline Wise) garage and pines for his engaged ex-girlfriend, Susan (Inga Schlingmann), an attorney at Margaret’s firm.

“It really was there from Day One,” Astin, 32, said of his rapport with Harden. “That’s not to say that it’s easy but I think it comes naturally to us because we’re both fearless performers so we’re not afraid to make a mistake.

“We came in at different times and were both offered the roles individually so it was kind of ‘Let’s see how this goes,’ he said. “I’ve always revered [Harden] and respected her work and we have a very similar compass because we’re both theater people — so I think there’s a very symbiotic connection there in the work and that comes across onscreen … in the humanness in the relationship at the center of the story.”

The multi-hyphenate Astin is no stranger to TV viewers; he played Greg in “Crazy Ex-Girlfriend,” Max in “Zoey’s Extraordinary Playlist” and Todd Eames on “Grey’s Anatomy”; his movie roles include “Pitch Perfect” and its sequel, “Pitch Perfect 2” (as Jesse Swanson) — on Broadway, he played Georg in “Spring Awakening” (among many other stage roles). He’s also an accomplished singer.

Astin said that the interplay between Todd and Margaret was there, on the page, from the get-go.

“I really loved [series creator] Scott Prendergast’s script for the pilot and was intrigued by the story and loved the mother/song relationship,” he said. “And, on top of that, I loved how messy Todd was and wanted to dive into his mind. I always find it really fun to play a character who’s on the outside looking in and goes the more unconventional route.

“Todd’s point-of-view is different than most people’s and it’s fun to play with that.”

Astin said that he and the show’s writers made some adjustments to how he played Todd once the series got over the hump of its pilot episode and into its own rhythm.

“I think they started writing toward me and giving me the freedom to improvise and add my own embellishments and flourishes to the scenes and to Todd’s physicality,” he said. “In the pilot, Todd wasn’t as physical as I’ve made him now, bumping into stuff, these happy little idiosyncrasies that make playing him delightful. It kind of takes on a life of its own.

“[Marcia and I] always do our homework and ask questions, like ‘What do you think [Todd and Margaret] did right before coming into this scene?’ In-between scenes we’re like, ‘What happened in the car? Why are we starting the conversation at this point?’

“That’s some of the nerdy stuff we’re into, but the delight is in the details.”

And, with a second season on the way, Astin said that Todd will undergo some changes of his own.

“I am aware of a few new elements coming Todd’s way,” he said. “I don’t think that all of the sudden he’s going to be a businessman — he’s always Todd no matter how successful or unsuccessful he is. I think Marcia and I have done a great job of establishing the bickering and argumentative nature of Margaret and Todd — but underneath it all there’s this layer of affection and love that can withstand anything.”