A full house even if she’s home alone

CATHERINE O’HARA is ready to laugh.

The comedian looks just as you’d expect her to -- oval face, pointed chin, large mouth that seems to be perpetually smiling. Her blue Irish eyes, plenty mischievous at 52, flash as ideas come over cappuccino at the City Bakery in Brentwood. In bursts, she apologizes if she’s not communicating with perfect syntax.

“I’m all inflection, no grammar,” she says, laughing at herself.

Since making her name on the “SCTV” series (for which she shared a writing Emmy in the ‘80s), O’Hara has appeared in more than 35 movies, including “Home Alone” and “Beetlejuice.” She’s now perhaps best known as part of the versatile ensemble of improv aces in Christopher Guest’s mockumentary films.

“He doesn’t limit you in any way,” she says of Guest. “That’s one of the genius things about him. He does not say no. You feel like everything you have to offer is worthy.”

O’Hara has created some of the most memorable characters in those movies’ affectionately oddball menageries. In “Waiting for Guffman,” her small-town aspiring actress earnestly explained how her husband was helping her ignore her instincts. As an ebullient housewife in “Best in Show,” she seemed to find extremely, uh, grateful male acquaintances from her past everywhere she went, to her mild-mannered husband’s consternation. In “A Mighty Wind,” her fading folk singer moodily warbled about catheters, accompanying herself on autoharp.

“It’s great to have people come up to me and say, ‘I hear [Guest] is doing another movie, are you in it?’ ” she says. “It’s nice that people care about what you’re doing.”

This month, O’Hara and the gang -- including Eugene Levy, Harry Shearer and Parker Posey -- can be seen in Guest’s “For Your Consideration,” about an independent film production that catches wind of Oscar rumors. While this one is not in the mockumentary format, it’s still entirely improvised except for scenes from the film-within-the-film, a World War II period melodrama in the American South called “Home for Purim.”

In “For Your Consideration,” which opens in L.A. on Nov. 17, O’Hara displays excruciating moments of hope and cathartic rants as the unheralded veteran actress Marilyn Hack, who sees herself as nothing more than a blue-collar worker until whispers of Oscar recognition work their magic on her.

“Until the door is opened, I don’t think she even flirts with that idea,” O’Hara says. “I think she did years ago, but now [she’s more] ‘I’m lucky to work, I’m not part of that world.’ ... She protests too much.”

As the second-youngest of seven kids, O’Hara comes by her humor naturally. “With a big family, you have to be quick and funny to get your word in at the table,” she says of her family in Toronto.

The actress says her mother is a great storyteller and her late father frequently told jokes. Her sister, Mary Margaret O’Hara, is a singer-songwriter; one brother was a company member in the Second City comedy troupe with Catherine and another brother is a writer. Their father was initially reticent about Catherine becoming an actress until “people at my dad’s job told him they’d seen me on TV. Dad was like, ‘Oh, OK, it’s a job.’ ”

Now, she and her husband, director Bo Welch, have two kids, who seem quite prepared to take over as family cutups. “My kids are very funny,” she says. “The other day ... I was getting mad at [my 9-year-old] and he was getting mad at me, and out of nowhere he said, ‘So I guess you’ll be taking care of yourself when you get old.’ ”

She giggles with impish pride at the precocious prophecy of vengeance. But despite her proclivity for laughter and the looseness of improvisation on the sets with Guest and company, O’Hara insists the ensemble rarely loses takes to breaking up.

“Because it’s improvisation, that moment will never happen the same way again,” she says. “The people you’re working with might come up with something so beautiful and funny, a beautiful gift from heaven, and if you laugh, you’ve blown that take.”

Although the dialogue is pulled out of the ether, the actors go through extensive preparation to flesh out their characters. So while much of O’Hara’s back story for Marilyn may never show up on-screen, her performance is informed by those submerged details.

“I wonder what [Marilyn] does at home, I wonder if she’s alone. Does she have a lot of cats? Except we don’t want to have a lot of cats on the set, so we [decide] I’m allergic to them and I’ll die if I’m near one, but I love cats so I have cat things all over my home,” O’Hara says.

Even in a comedy, that approach lends a realism to the proceedings that can make her character’s ups and downs painfully authentic. She’s delighted to squeal on her husband for crying when he saw the movie -- both times.

“I haven’t made him cry enough!” she declares, laughing.