Marcia Gay Harden and Skylar Astin on Their Mother-Son Dynamic in CBS' 'So Help Me Todd' (Exclusive)

The duo star in CBS' freshman drama, which debuts Thursday, and only ET was on the Vancouver set.

Marcia Gay Harden and Skylar Astin star in CBS' new drama, So Help Me Todd, which follows razor-sharp attorney Margaret Wright, who hires her talented but aimless son, Todd, as her law firm's in-house investigator. ET was first on the Vancouver set in August, where Harden and Astin previewed their series, which premieres Thursday.

"Dynamic duo, that’s us," Astin told ET's Lauren Zima on the So Help Me Todd set in August while they were filming episode 3. "I love working with Marcia. I love sparring with Marcia in the scenes. She comes from such a smart place. She’s also a thespian like myself, so a lot of the times the scenes kind of play off like theater. We’ve done this thing -- technical term is to cross-shoot meaning that they'll be filming you while they’ll be filming me at the same time -- so it cuts together quite nicely and we really get to live in that space and what was actually happening on the day. It really has that feel."

Harden acknowledged that being a mom herself has seeped into her onscreen persona at times, especially when it comes to certain pieces of dialogue. But the mother of three shared she takes a different approach to mothering than her character does. 

"I’m a different kind of a mom. I think Margaret’s a little more, what is the word, she’s slightly grander. She’s a little more old school in a way," the 63-year-old Oscar winner said.

For Astin, the initial draw to the show -- aside from working side by side with Harden -- was "the snappy writing."

"[Creator] Scott Prendergast wrote a great script. I was in from page 1," the actor credited. "Todd is so flawed and such a black sheep and such a wild card renegade, and I love playing him. I love everyone that surrounds him. I love the environment of Portland, which is our backdrop for the show, and it’s just an adventure. It's a drama but really, I kind of approach it as a dramedy. If anything, it leans more towards a comedy."

Bettina Strauss/CBS

Don't expect Astin, who starred in the musical dramedy Zoey's Extraordinary Playlist, to belt out into song on this show. "I am excited to show people that I can do that, and it is a superpower and I love it and and when in Rome I do -- and I mean singing -- but I really do love playing this dark twisted comedy," he said, adding that he still sings in between "action" and "cut" on set. "That's what I was telling the crew. 'Are we going get to see you sing a lot, Todd?' You will not get to see me in between the tapes, but I will constantly be signing. That’s just how I live."

And though the journey has only begun on So Help Me Todd, Harden has been having a fun time living in this world. "You're an actor and it goes like this, up and down and up and down and when you're down, you never think it will go back up. But when you're my age now and it goes [up], you just have such a beautiful moment. You just cherish it," she reflected. "I'm remembering this 'cause I know the way of a wave and I'm going to cherish this surf for a while."

Harden is halfway to officially joining the EGOT club. (She has an Oscar for Pollock and a Tony for God of Carnage.) Asked how she'd feel if she was able to get one step closer to that rare accomplishment, she admitted, "I’d feel really, really, really good. That would be so fantastic." Though she lost out on the Emmy this year, for which she was nominated in the Guest Actress in a Drama Series category for The Morning Show, Harden already has a place for the honor should that day come.

"I do have a bookshelf with the Oscar and the Tony and I think I would put it right next to it," she forecasted.

As for why viewers should tune in to So Help Me Todd, Astin had the, ahem, perfect pitch. 

"The reason why you should tune into So Help Me Todd is you're going to get comedy, you’re going to get adventure, you’re going to get great cases, great turns. You’re going to also get a lot of family, and with that family, a lot of drama," he teased. "But there's also a ton of comedy and even a bit of heart because at the end of the day, even though people are at odds, they cannot help but care for each other."

So Help Me Todd premieres Thursday, Sept. 29 at 9 p.m. ET/PT on CBS.