NEW YORK -- The new Showtime drama "Shameless" overflows with its boozy, heedless father and the six unsinkable kids who care for him and one another. William H. Macy ("Fargo," "Door to Door") plays the shiftless grifter dad. As Frank, he is abrasive, self-absorbed, manipulative and delusional.

"I'm the father, teacher, mentor, captain of our little ship," Frank pridefully rants to the family in an early scene, reminding them of what he deems "the most important thing in this life: partying."

In more ways than one, Frank is blind drunk.

But the family sticks together and gets by with pluck, defiance and no apologies -- that is, no shame. Not even shame from the children for their father, whom they often have to step across, passed out on the floor.

"It's not like they forgive him for his behavior," says Emmy Rossum, who plays Fiona, the oldest of the brood. "They just hope that, one day, he will get better."

In the absence of a real mother, Fiona is the family's surrogate mom. Think: Wendy, if Neverland were a tumble-down row house in blue-collar Chicago, with Peter Pan relying on alcohol and chemicals to fly.

"Shameless," which premieres Sunday at 10 p.m., is based on the British series of the same name created by Paul Abbott ("State of Play"). It's a potent cocktail -- outrageous, heartbreaking and heartbreakingly funny. It may also be the first TV series whose opening title sequence focuses, unflinching, on the household's highly trafficked bathroom.

"It's easier to identify with a family that has real struggles, be it financial or emotional or whatever, than a show that glamorizes what life is like in this country right now," Rossum says. "A lot of shows on TV are escapist in that way, but I think ours is definitely different and grittier, with the humor coming out of real situations. I think that's what will be relatable to people."

The diverse offspring (do any of these siblings share the same mother?) range from a dark-skinned toddler to the 20-ish Fiona, played by Rossum with poignancy and fire.

"She is a rough, working-class, kind of feral character," says Rossum. "She's very outwardly aggressive. She's got this inward vulnerability and yearns for affection, but you don't see that a lot."

Nor do you see much glamour, never mind that Fiona -- with the luminous hurt eyes and furrowed brow -- is gorgeous.

"Fiona is the kind of girl who doesn't have time for hair and makeup, or probably even a brassiere," Rossum says. "She gets up in the morning, throws a shirt on, and goes to feed the kids."

Between the child-care demands and her odd jobs to help pay the overdue bills, Fiona barely even has time for the hot romance with her roguish suitor, Steve (Justin Chatwin), whom she meets at a club on a rare night out. She keeps him guessing. The audience, too.

"As an actor, to play an underlying feeling and then cover it up with another is the most fun," Rossum says.

She has won high praise from her co-star who plays the series' pickled patriarch.

"Really, the heart and soul of the thing is Emmy Rossum," Macy says. "She does the heavy lifting on our show."

Rossum, 24, came to "Shameless" with a crowded resume including the films "Poseidon," "The Day After Tomorrow" and Clint Eastwood's "Mystic River," in which she played Sean Penn's daughter.

She starred as Christine in the 2004 film version of "Phantom of the Opera," where she displayed the singing voice -- described as "angelic" -- that had launched her career in show business in the first place. When she was 7.

Growing up in New York, she was sent by her music teacher to the Metropolitan Opera to audition for the Children's Chorus. She went on to appear in some 20 Met productions.

In the 2000 indie film "Songcatcher," she played an Appalachian girl with a gift for folk music. In 2007, she released her debut album.

Now on "Shameless," though, any vocals are mostly kept off-camera: "Bill Macy brings his ukulele to set and we make up funny songs -- dirty songs," Rossum says with a laugh.

"There's one scene later in the season where we discover that Bill's character can play the piano, and we're all singing 'I Will Survive.' But I was instructed to sing poorly."