Some of the best onscreen chemistry on "Lost" involves one of its youngest actors and its leading lady.

William Blanchette, a 31/2-year-old boy cast as Aaron, spends a lot of time opposite Evangeline Lilly, the dark-haired actress who plays Kate. Whenever the Kahala boy sees "Evie," it's all hugs and kisses.

Lilly knows how to direct William better than anyone, said the boy's mother, Natasha Blanchette. Her son used to work for pickles, but now he works for Lilly's "airplane" rides.

"When the director yells 'cut,' the crew are quick to take a couple of steps back as Evie sweeps William off his feet and proceeds to twirl and whirl around the set with him held over her head," Blanchette said. "She is unpredictable and Wil- liam thinks that is hilarious. She is just so sweet."

William has played baby Aaron for several seasons, growing from infant to toddler on both "Lost" and in real life. That's him in one of the online "sneak preview" trailers for this season, wide-eyed as FBI agents come to the front door of the home where he and Lilly's character, Kate, are living.

Even though Lilly does not have children, she has an easy way with William, said Blan- chette, who also has two older girls.

"You can't fake it with kids," Blanchette said. "She is just instantly in tune with whatever he is up to. I will go through a scene with him at home, but when we get there, she is the one who evokes the performance from him.

"The director will look at Evie and say, 'Can you get him to do this?' and she gets on her hands and knees and says, 'Come on, William.' "