The Sisters of Perpetual Abstinence

It's fun to walk down a Los Angeles street flanked by Mary-Kate and Ashley Olsen. First you have to get over feeling like Andre the Giant as you clomp alongside them, because they are small -- Mary-Kate is five feet one, Ashley five feet two, both a size zero. They dart gracefully through passersby like a pair of dragonflies, while everyone else seems to lumber.

What's entertaining is to watch people's faces as the girls head to a favorite breakfast place, the annoyingly named but tasty Urth Caffe. They all do a triple take. What registers first is: Hmm, twins. Next: Pretty twins! And finally: Are they...?

As the two enter the cafe, a pair of college-age guys give them the up-and-down. "God, they are hot," one breathes.

"I'll take the one on the left, you take the other," says his pal. They stay rooted to the spot, of course. In the meantime, an eight-year-old girl, who has the stunned look of Wile E. Coyote after the anvil lands on his head, approaches for an autograph.

"Of course!" they say in chorus. As they chat with their trembling admirer, the two do not even notice their older fans, who watch them, mouths slightly open, hands dangling at their sides.

Famous since they were nine months old, the Olsens, now seventeen, are like your friend's heretofore-unnoticed kid sister who has suddenly grown up. Because they seem to have lived a charmed life, are reportedly worth $150 million each and are largely absent from the usual E! network red-carpet hoo-ha, there is an aura of tantalizing mystery around them. Or perhaps it's just sheer nose-against-the-glass curiosity: This year the mary-kateandashley brand will move a projected $1 billion worth of merchandise. Bars and Web sites feature a countdown to their eighteenth birthday. ("Find out if the twins are already legal in your state!" says one site. "Avoid pesky jail time and legal fees!") Howard Stern mentions them on the air regularly and enthusiastically.

Still, seventeen is a dangerous age for a child star -- not to mention a child mogul. In some ways, it's easy to craft an image of ideal girlhood. Almost everyone agrees that little Missy should be sweet and spunky and pretty. But once you get to be eighteen, everybody has a different idea: One part of the audience might have gone goth; the other might have taken the cheerleader route. The idea is to slowly turn Mary-Kate and Ashley into actual movie stars without alienating their young fans, who once crowded 20,000 strong into Minnesota's Mall of America when the twins made an appearance, chanting, "Olsen! Olsen!" as the floor vibrated and seven bodyguards attempted to keep order.