"I used to live in Kakadu, which is in Jabiru," Isabel Lucas announces outside the Griffith Observatory in the Hollywood Hills. Although we've met here to go hiking, the 24-year-old actress speaks the gibberish-sounding place names so nonchalantly that it's momentarily plausible that she's referring to a distant planet and has chosen the observatory to make contact.

Lucas is an earthling—and an earthy one at that—born and raised in Melbourne (with stints in Queensland, Switzerland, and Australia's Northern Territory), which means she's not an alien in the extraterrestrial sense. She is, however, way out there. "Quirky" by her own admission, she says she likes to hike in Griffith Park because of the "energy of the trees and air." At the sight of an overturned trash can, she launches into a lengthy discourse on the differences between jackals and dingoes. And though there's an outstanding arrest warrant for her in Japan (the result of an anti-whaling protest she participated in), Lucas seems entirely unconcerned about the fact that the world premiere of her new film, Transformers: Revenge of the Fallen, will be held in Tokyo. "Oh," she says, "it's quite unlikely I'll be arrested."

Kakadu, it turns out, is an Aboriginal community where Lucas lived for a year during her seminomadic, bohemian childhood. "My best friend was Aboriginal," Lucas says. "She taught me about 'bush tucker'—the food of the land, the different things you could eat if you got lost in the bush, like grasses and berries. There's this tree called the billygoat plum—the fruit is quite nice. It'd be a whole different story here. I don't recognize any of these plants," she adds, surveying the local foliage.

In fact, Lucas is dressed as if she's never been on a hike in her life—a faded green eggs and ham T-shirt, wide-leg jeans, and green suede ankle boots. Her style is hippie-chic, but her face is pure Swiss Miss, a look she owes to her mother. "Mom spoke to us in Swiss when we were little," she says—she calls the "singsongy" German dialect her first language.

Tourists on the trail don't give her a second glance. If they were Australian, however, they might recognize her from the megapopular soap Home and Away. If they were avid gossip-rag readers, they might peg her as Entourage star Adrian Grenier's ex-girlfriend, or as Transformers costar Shia LaBeouf's mystery passenger when he flipped his truck and was cited for DUI last year (no charges were ultimately filed). The tabloids did their best to link her breakup with Grenier to a relationship with LaBeouf. "I don't think it's unusual to spend time with your castmate," she says. "People instantly assume you can't have a platonic friendship with someone of the opposite sex. I think this may be specific to L.A.—or America." What's clear is that Lucas, who is single, is as unrestrained in her affection for LaBeouf as she is in most things. "He's got an awesome sense of humor and a big heart," she says. "He's got a lot to give. A really interesting character. And he's also very passionate."