Judy Greer is quite the character

You know you’ve seen her somewhere. She’s funny, she’s (usually) a redhead — maybe she’s Kathy Griffin? No, not her.

Who is she? That actress who has been in a million romantic comedies? Always the sidekick? You must know her name.

Judy Greer knows this is what strangers think when they pass her on the street. Some end up discreetly pulling out their iPhones to Google her, but others just walk straight up to the actress to ask her what she’s appeared in.

“I Don’t Know What You Know Me From,” is what she wants to say. That’s also the title of her new book, in which the 38-year-old candidly describes what it’s like to be a character actress in Hollywood — successful but not quite a star. Even though it’s how many actors make their living, it’s a career path that’s rarely discussed, warts and all; playing supporting roles may pay the bills, but it doesn’t make you famous.

“For a long time, I think my family thought I was living in a $3-million mansion in the Hollywood Hills,” said the Michigan-born Greer. “I got the sense that they don’t know what it’s like to be a working actor — they know the pictures in the magazines. But having a job as an actor doesn’t mean that you made it.”

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Apparently, not many people get what Greer does. In her book of essays, she chronicles the oft-ridiculous things she’s asked in public. Why didn’t she have a role in the 2011 hit “Bridesmaids”? (She auditioned; she didn’t get a part.) What’s Charlie Sheen like? (He put a lit cigarette out in her coffee on the set of “Two and a Half Men.”) And perhaps most offensive: “How come you haven’t starred in a movie yet?”

It’s “not like there’s an audition form with star and co-star boxes and I keep accidentally checking the co-star box,” she writes. “Maybe I’m not good/funny/pretty enough?”

She’s nothing if not honest — sometimes brutally so. When she arrived for an interview at La Brea Bakery last week, she was still heavily made up from a morning shoot for her Yahoo Web series, “Reluctantly Healthy.”

“I never wear this much makeup,” she said, eyeing the menu. She reluctantly decided to order the bread with her soup, admitting she only allows herself to eat carbs one day a week.

“The truth is,” she continued, “if I was maybe better or funnier or prettier, wouldn’t I have starred in a movie? ... I can see it objectively as a businesswoman — if no one’s buying your product, then there’s not a desire for it.”

But to be sure, there is demand for Greer. She’s appeared in more than 30 movies and over two dozen television shows, typically providing much-needed comic relief. As she puts it, she usually serves as the “blue-collar bestie” who makes impossibly beautiful leading ladies like Jennifer Aniston or Katherine Heigl seem more relatable. She has played the BFF role so many times — in “Love Happens,” “27 Dresses,” “13 Going on 30” — that her husband jokes she should gift each new co-star with half of a heart-shaped best-friend necklace.

This wasn’t what she set out to do. After getting a bachelor of fine arts degree from DePaul University’s theater program, she moved to Los Angeles and began auditioning for lead roles. But she kept getting passed over for, as she puts it in her book, “Pretty McPrettyson,” so she started reading for “Pretty’s best friend/sister/assistant.” As it turned out, her goofy sense of humor and approachable look made her the perfect supporting player.

It’s a reputation that’s been hard to shake.

“People in Hollywood want you to lead them to the water,” said Anne Fletcher, who directed Greer in “27 Dresses.” “Where do you put Judy? She’s so unbelievably funny but she’s also a great straight actor. She’s very beautiful in a very normal way. So some people get confused by that and what to do with her.”

In an effort to stop the typecasting, Greer said she still auditions for roles — something stars with bigger egos often refuse to do. She’s even written letters to filmmakers whose projects she feels particularly passionate about, urging them to consider her.

“Sometimes you have to put it all out there,” said Greer, whose dream role would be akin to Meg Ryan’s in “When Harry Met Sally.” “If a director is torn between two actresses for something, maybe my letter will be the thing that will make him say, ‘Oh, I’ll go with Judy Greer.’ ”

Her enthusiasm helped her land a part in July’s “Dawn of the Planet of the Apes,” in which she plays a primate rendered on screen through performance capture technology.

“Somebody told me Judy Greer wanted to come in and I was like, ‘You’re kidding!’ Because it’s not a huge role, but it’s an important role,” said “Planet” director Matt Reeves. “And then she came in and started pitching me, talking about how obsessed she and her husband were with ‘Planet of the Apes.’ She became very emotional. And when somebody comes in and they’re really passionate, it makes a huge difference.”

Of course, when the red carpet is rolled out for the big-budget film’s premiere this summer, Greer doesn’t expect to be treated as a main attraction. In one bittersweet essay in her book — released earlier this month — she recalls posing in front of a step-and-repeat and being ignored by photographers. The shutterbugs were more interested in taking pictures of her “Arrested Development” co-star David Cross’ wife, actress Amber Tamblyn, even though Tamblyn wasn’t a part of the series.

“I’m here! I’m standing in front of you people! I’m in this!” Greer said she remembers thinking. “You go through all the trouble and you get your makeup done and you get your hair done and you hire a stylist to put yourself in something very pretty — and if you’re me, and you’re shy, it’s already hard.”

Sure, it can be upsetting, but she’s used to swallowing her pride. She knew, for instance, that at the press junket for “The Descendants,” no journalist would want to hear about her profound acting experience on set. But they ate up the fun anecdotes about George Clooney pulling pranks on his fellow cast members.

“You just tell them what they want to hear,” Greer said with a shrug.

But Jennifer Garner, who starred in “13 Going on 30” with Greer a decade ago, feels her co-star’s moment in the spotlight is imminent. The actress, who gave Greer’s book a blurb to help promote it, said her fellow cast member’s presence on set of the romantic comedy made “everyone seem funnier than they really were.”

“She’s not afraid to be a real goofball, but she’s not someone who is trying to take up all the oxygen in the room,” Garner said. “She’s smart at playing those best friends roles, but the reality is that she is a leading lady. And we’re going to see that more. People say she’s a character actress, but she’s just an actress who has been smart enough to move around and do different things.”

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