Cates may never act again, but she can live with that: after all, she has never acted before. The same goes for Hiep Thi Le, a 22-year-old pre-med student at the University of California, Davis. Le hadn’t considered a life in pictures, but found herself carrying Oliver Stone’s Vietnam epic “Heaven and Earth” on her exceedingly narrow shoulders. Stone cast her because “she was so unspoiled.” And that’s precisely why directors have taken the trouble to make stars from scratch. Directing nonactors, says Neil Jordan, whose “The Crying Game” made an Oscar nominee out of fashion assistant Jaye Davidson, “is like working with a child. There’s a sense of reality there. There’s no technique.”

Accidental actors have always peopled the movies–Harold Russell, the sailor in “The Best Years of Our Lives,” even won an Oscar. But lately they’re everywhere. There’s the teenager who falls in with the mob in ‘A Bronx Tale" (Lillo Brancato was discovered while swimming on New York’s Long Island), a methodical IRA terrorist in “In the Name of the Father” (Don Baker is a musician) and a steadfast dad in “Philadelphia” (the Rev. Robert Castle is Jonathan Demme’s cousin). Hollywood may turn these lives around, or merely upside down. Still, there’s something reassuring about stories like Cates’s and Le’s: they confirm our suspicion that sooner or later, somebody will swoop down and make us all movie stars.

“Gilbert Grape” writer Peter Hedges spotted Cates on one of those “Sally Jessy Raphael” segments: overweight women who never leave the house. Cates, 46, grew up in the Texas panhandle and married at 15. By the ’80s, her weight and arthritis made it all but impossible to walk. “I didn’t want anyone to see what I had become,” she says. “I lived my life ruled by what other people thought of me. I’ll never do it again.”

Sixty women were considered for the role of Momma, including some 300-pound actresses who were apparently willing to gain weight for the role. By the time Cates read for Hallstrom, she’d had a felicitous introduction to Prozac; taken correspondence courses for her high-school diploma and gotten her self-esteem in working order. “Everyone kept reassuring me that I could do it,” Cates says of the role. “I said, “Don’t let me go make a fool of myself!’ But Peter and Lasse knew what I wanted Momma’s role to say: a person’s value doesn’t have a thing to do with their weight.” Cates gives the moving, complicated performance of a woman who’s been there.

Hiep Thi Le has been there, too. She was born in Vietnam. In 1978, her family began fleeing the country in stages: Le and a younger sister soon joined the “boat people” bound for Hong Kong and spent three months in refugee camps. The family was finally reunited in Oakland, Calif., in 1981. Three years ago Le tagged along when an older sister went to an open casting call for “Heaven and Earth” and made a videotape as a lark. When she was cast as Le Ly Hayslip (who wrote the books on which the movie is based), her main concern was justifying Oliver Stone’s faith in her, proving that “even if I was a mistake, I was a good mistake.” For all the drama of Le’s childhood, there’s something innocent about her. That naivete is unexpected: Le has pulled off a shocking, strenuous role, spanning three decades and a couple of continents, enduring torture, rape and warfare. Stone says the subject matter convinced him a nonprofessional was right for the part. “It’s about a woman who’s overcome a lot of suffering,” he says. “What did you want to do? Put in Julia Roberts?”

Out of obscurity: What happens, though, to people plucked out of obscurity? “All the attention and pressure of a movie can disturb people’s lives tremendously,” says Jordan. “Afterwards, it can be quite negative.” Last year Jaye Davidson said he intended to go back to being a fashion assistant; now he’s reportedly planning to make a sci-fi flick called “StarGate” and spending $45,000 a month on jewelry and clothes.

Cates and Le seem to be in good shape, if only because they have no expectations. What Le is really concerned about is getting into med school. Cates has been approached by a talent agency: “I said, ‘I will not be a sight gag for anybody. I will not do anything degrading to myself or to other fat people.’ They still wanted to sign me, so I’m considering it.” For Cates, acting seems to have been therapeutic and thrilling. Of course, there was that Los Angeles Times reviewer who referred to Momma as “horrifically overweight.” Says Cates, “That hurt. She has a massive command of all these words and she chooses a negative phrase like ‘horrifically overweight’.” Cates certainly deserves better. Maybe the word the reviewer was looking for was grand.