Isla Fisher’s voice is hoarse from coughing, and the tip of her nose is red. She looks around for a tissue. “Do you think I can use this?” she asks, holding up her napkin. It is the extra-thick restaurant kind—paper masquerading as cloth. “I guess they’re not going to recycle it, huh?” Sitting in a vinyl booth at a faux-retro diner, Fisher explains that she spent the past week in bed with a cold at her rented Los Angeles home, reading chick lit (“one of those Shopaholic books”). The Australian actress (whose first name is pronounced “eye-lah”), best known for her performance as a nymphomatic hellcat in 2005’s Wedding Crashers, says she rarely dips into the genre. Then, after a moment, she confesses that she has actually contributed to it in a way, writing two teen romances, Seduced by Fame and Bewitched, when she was a teenager herself.

It takes only a few minutes in Fisher’s presence to know that she is neither a high-maintenance diva nor a flighty starlet—nor really any of the usual sorts of creatures that emerge from the wilds of Hollywood. This is not just because she is a published author who blows her nose on a napkin. Or because she orders a chicken sandwich with bacon and mayonnaise and fries. Or even because she is engaged to the enigmatic, notoriously un-Hollywood British comedian Sacha Baron Cohen. It is because absolutely nothing about the 31-year-old actress—from her teeth to her amber-colored hair to her affable manner—seems over-bleached, over-processed, or over-considered.

Fisher’s normality is especially disarming if you’re at all familiar with her screen incarnations—particularly Luvlee Lemons, an ex-stripper who seduced a brain-damaged man in last spring’s The Lookout, and, less recently but more memorably, Gloria Cleary, the shrill vixen who terrorized and bewitched Vince Vaughn’s Jeremy in Wedding Crashers. “I’ve played some pretty wackadoodle people,” Fisher says. “I really hope that I’m not channeling any subconscious ideas about myself.”

In her latest role, Fisher forgoes pathology to play someone more subdued. Hot Rod, directed by Saturday Night Live writer Akiva Schaffer, is about an Evel Knievel type named Rod Kimble (played by SNL’s Andy Samberg) who, in order to save his stepfather’s life, must jump 15 buses with his motorcycle. Fisher plays Kimble’s girlfriend, Denise—the female version of a classic straight man. This, Fisher says, required her to “just stand there and roll my eyes.” But Schaffer insists that Fisher gave the “flat, girl-next-door part” a compelling depth: “You can feel that tinge of intelligence behind her eyes. The way she says things or the looks she gives, you can see there’s more there.”

If, as seems likely, Fisher taps into that “more” and becomes a comedic actress on par with her idols Lucille Ball and Goldie Hawn, it will be thanks to two forces—the first being her Girl Scout—like resourcefulness. “The reality is, for women in comedy, there aren’t many opportunities to be the funny one,” she says. “There aren’t scripts written. If you want to be challenged and do the work you want, you have to create the material yourself.” She’s collaborating with Amy Poehler (Saturday Night Live, Blades of Glory) on a screenplay for a film called Groupies, in which the two will play “two overconfident dum-dums” obsessed with a band that doesn’t know they exist, and she’s helping to produce Cookie Queen, in which she’ll portray a woman who aggressively competes against a little girl in a cookie-selling competition. The second force is Cohen. When auditions for dramatic roles were yielding offers for parts like “redhead” in Dallas 362, Fisher says, “Sacha was like, ‘Why don’t you go funny?’” That’s when she auditioned for Wedding Crashers.