Back in town to boost interest in their new ABC sitcom “Downward Dog” (previewing at 8:30 p.m. Wednesday on WLS-Channel 7, then moving to its regular Tuesday slot on May 23), Andersonville native Lucas Neff and former Chicago resident Allison Tolman made it clear that their canine co-star was key to making the new series work.

“The dog frames the story,” said Neff, who finished a five-season run on Fox’s “Raising Hope” in 2014. “The dog is what it’s all about.

“If nothing else, if we’re back for a second season, that dog has more of a lock on being back — even more than Allison and me,” he said with a big laugh, which Tolman joined in.

In “Downward Dog,” Tolman (“Fargo”) plays Nan, a thirtysomething woman who struggles to balance her personal life and traumas with the frustrations of her job — made difficult by her self-absorbed, jerk of a boss (Barry Rothbart). Neff plays her ex-boyfriend, whom she still sleeps with on a regular basis.

The key thing here: Martin the dog (voiced by Samm Hodges, the show’s co-creator) is the lonely but frequently insightful narrator, who drives the storyline in each episode. Martin is totally devoted to Nan, who loves her without reservation — though he has a lot of reservations about how much he’s left to fend for himself during the day.

The stars were delighted to learn that their canine co-star, whose real name is Ned, was found at Chicago’s own PAWS shelter. “He was cast just from his headshot,” quipped Tolman. “We just got lucky that his adorable face and expression in that photo turned out to be just what was needed.”

Neff joked that “Ned also proved that being an actor is not all that tough. I mean, he’s a dog, and he was trained perfectly to do what he has to do in this major television network show — and he did it in six weeks! So much for going to NYU or Juilliard theater school,” said Neff.

Even a short visit to Chicago takes the actor back to their early career years, before they found fame. “Every time I come back to Chicago I have to get on the L,” Tolman said. “I was a Brown Line girl, so I really try to take a ride. … It’s really the best way to see Chicago and its neighborhoods.”

Neff, a Whitney Young High School and UIC grad, added that he was delighted he was able “to squeeze in a Sox game, and to discover a new restaurant off the beaten path,” noting an “amazing meal” he had at a new Korean barbecue joint on Ashland Avenue.

As for getting along with Ned/Martin, Neff said “that was something I didn’t have to work on. I have five dogs at home — all strays, all adopted. But, unlike Ned, they all have many more crazy issues than he has!”