SHERMAN OAKS, Calif. — The gals who play the two broke girls are cracking each other up.

As their interview takes place in late July, Beth Behrs and Kat Dennings can count a grand total of one week spent working together. That was when they filmed the pilot for “2 Broke Girls” — and that was in April.

But over breakfast at Mel’s Drive-in, a Valley landmark, they share laughs and a chemistry that seems years in the making, just as they do on their sassy new comedy as struggling waitresses at a Brooklyn greasy spoon. (“2 Broke Girls” premieres at 9:30 p.m. Monday on WCSC before settling into its regular slot at 8:30 p.m. Sept. 26, hammocked between the CBS hits “How I Met Your Mother” and “Two and a Half Men.”)

While waiting for production to resume in early August, they solidified their friendship.

Kat: “We’ve been checking in with each other every few days.”

Beth: “I’ll randomly text Kat about something I’m watching on TV in the middle of the night: ‘You need to see this!’ ”

Kat: “Like, “ ‘Extreme Makeover” did WHAT?!’ ”

No actorly exchanges about process or technique?

“Oh, no!” Beth laughs. “We don’t talk about work at all.”

“Should we?” poses Kat, her eyebrow raised.

Orders are taken. Beth chooses an omelet and hash browns. Kat calls for wheat toast and, more urgently, a cup of joe.

“Nectar!” she rejoices when the coffee arrives. “And it’s not bad.”

“I like diner coffee,” Beth agrees as her cellphone sounds off.

“Oh, gee,” she sighs after checking the number displayed. “This guy has been calling me all morning. I don’t say my name on my message, so maybe he thinks I’m someone else. He keeps leaving these intense, long messages.”

“Let me do it, let me do it!” says Kat, eagerly snatching the phone and, in the guttural tone of a longshoreman, growling into it: “WHAT!!! Who IS this? WRONG number! NEVER call again!!!”

They both dissolve into laughter. “That makes me SO happy!” Kat giggles.

On “2 Broke Girls,” their characters will form a similar bond. But not instantly. First, they have to size each other up.

Kat plays sarcastic, street-wise Max Black, who, to make ends meet, must work two jobs, one of which is the night shift at the downtrodden Williamsburg Diner.

Beth plays chic Caroline Channing, whose ritzy Upper East Side lifestyle has abruptly come undone after her money-manager father was busted for financial shenanigans. Like Max, Caroline is now broke, too, and is seeking refuge at the diner working alongside Max, who warily receives her not only as a co-worker but as a flat-mate, too.

So not only is “2 Broke Girls” a buddy comedy, it’s also a fish-out-of-water sitcom, with Caroline the Brooklyn-beached fish.

The dialogue is snappy, befitting the show’s topflight creative team: Michael Patrick King (“Sex and the City”) and Whitney Cummings (TV’s comedy “It” girl who is represented on the fall schedule by this show as well as her new starring sitcom, “Whitney,” on NBC).

But beyond its writing, the charm of “2 Broke Girls” comes down to its two leading ladies.

In playing their roles, they both speak of trying to avoid stereotypes.

“Caroline is a girl who used to walk out of her New York high-rise with a car waiting and someone there to hand her a Starbucks,” says Beth. “For me to play her, I had to find the entitlement.”

“Caroline’s really sweet and innocent and adorable,” Kat says. “I think that’s a fresh approach.”

“And she’s smart,” Beth adds. “She went to Wharton business school. I don’t think Max would have taken to her if she weren’t smart.”

“Max is more and more impressed with Caroline as she gets to know her,” Kat agrees.

“And because Max takes a liking to Caroline, it shows she’s more than a tough cookie,” says Beth.

Both actresses are 25 and hail from Pennsylvania. But there are distinct differences.

Beth, whose credits include theater as well as the feature films “American Pie: Book of Love” and the upcoming indie comedy “Serial Buddies,” is a whippet-slender blonde with an unexpected past playing competitive soccer in school.

Kat is a curvy brunette with smoldering eyes and alabaster skin. Her list of films includes “The 40-Year-Old Virgin” and “Nick and Norah’s Infinite Playlist,” and, a decade ago, she played Bob Saget’s teenage daughter on his short-lived TV comedy “Raising Dad.”

Despite the sexy Mutt-and-Jeff contrast they strike, the two women, curiously enough, stand about the same height.

“I’m 5-feet-5,” Beth reports. “But the shoes make me 6 feet. Those beautiful Louboutins! But when I was wearing them, it was really hard not to hang on to Kat because I’m really clumsy.”

“I’m just under 5-feet-4,” Kat says. “But Beth and I are on such different scales: She’s on a Barbie scale, and I’m on a G.I. Joe scale. My head is like two times the size of her head!”