LOS ANGELES, MARCH 1 -- Today, at the midpoint in their Southern California tour, Britain's Duke and Duchess of York finally got to do something they specifically asked to do -- see the real thing, which is to say the fake thing: a special-effects film studio called Showscan. They spent the morning playing with movieland toys: a fake whiskey bottle, fake bullets shattering glass, a fake screaming roller-coaster ride and a fake car plunge down an icy Alpine road.

Were they having fun yet?

Ask the Duke of York, who began the two-minute film-and-motion simulated thrill-ride on a roller coaster with regal aplomb, his arms coolly folded, leaning casually back in his chair on the eight-seat ride.

But within moments, he was clutching the railing, even letting loose a little shriek, a companion said, as the device careened wildly in synch with the film in front of him.

The "hot seat" ride is not advised for heart patients and pregnant women, and Showscan President Roy H. Aaron said the duke signaled "no" to the pregnant duchess after his first wild roller coaster ride. So from her red director's chair, the duchess, wearing a gray double-breasted suit and gray-trimmed ivory hat, called out, "You want to go again? . . . You looked very funny."

He agreed gamely. She rubbed her gloved hands with relish, urging the operators with a wicked smile to "Take him for a real spin . . . nice and fast -- a bit of action." The seats plunged and dipped with the 90 mph. sensation, and when the shaking stopped and the riders "plowed" into a snowbank, she asked brightly, "You all right?"

If Southern Californians have spent four days pressing their noses against the glass cordon of royal fantasy, Tuesday was the royals' turn to marvel at the fantasy that movie wizards dish out.

"I want to see what Fergie really looks like -- on TV you can't tell," said secretary Veronica Ancrile, whose boss answered the phones so she could catch a glimpse. "We see people shooting movies all the time, but this is special."

It was what the Yorks had been waiting for.

In what is becoming a bit of royal "shtick" almost as common as christening ships (Diana, the princess of Wales, recently coshed Prince Charles on the head with a gimmick bottle), executives demonstrated an ancient bit of movie business: whacking someone with a harmless resin-bottle. Then they waited for Sarah's puckish nature to take its course.

"That's what you've been waiting for me to do, isn't it?" Aaron said she remarked, when she was handed a resin whiskey bottle. Instead of walloping Andrew, she said, "Sean, where are you? ... Come here."

Lt. Col. Sean O'Dwyer, her private secretary, stepped up dutifully. "Does it really hurt?" she asked, before smashing it over O'Dwyer's head. "It's quite all right," said O'Dwyer, with courtier-like aplomb.