And not just because she’s the most unforgettable commercial star since Clara Peller went searching for beef. The fact is, Eisenberg has upstaged half of Hollywood. As the ventriloquist-like Pepsi Girl, she’s gotten the better of Marlon Brando, Aretha Franklin and Joe Pesci. She turns in the most affecting performance in Sally Field’s film “Beautiful,” where she plays the daughter of a beauty queen. This week Eisenberg goes for the hard stuff. She’s starring as Helen Keller in ABC’s remake of “The Miracle Worker.” Those of you dying to pinch her dimpled cheeks are in for a shock. As the deaf and blind Helen, Eisenberg turns in a fiery, painful, anything-but-cute performance, complete with the nastiest food fight in recent memory. We always knew she was a charmer. Turns out Eisenberg is a pretty fierce actress, too.

Eisenberg may weigh only 51 pounds, but she takes her job seriously. To prepare for “Miracle Worker,” she visited schools for deaf/blind children. She also learned sign language. “I got kind of addicted to it,” Eisenberg says. “I would go into stores and would sign to them, ‘Do you have this?’ They would look at me like this”–and then she does kooky things with her Raggedy Ann eyes. It’s easy to forget that Eisenberg is a kid. She speaks in perfect sentences and is so polite that she won’t touch the M&Ms her mom put out for the reporter. She’s even writing a screenplay. “It’s called ‘Three Generations’,” she says. “It’s a relationship movie.” That said, Eisenberg is refreshingly normal. She goes to public school in New Jersey. She makes her bed and helps with the dishes. “I’ve seen a lot of kids whose parents have the notion they’re going to be a star, and everything is oriented towards that,” says mom Amy, who produces community theater. “If all this ends tomorrow, that’s OK.”

There’s little danger of that. Eisenberg has been acting since she was 3–she was discovered by the agent for her brother, Jesse, star of TV’s “Get Real”– and she loves it. “Doing movies is kind of like a vacation,” she says. Not that it’s always easy. Elliott, who plays the stern but loving teacher Annie Sullivan in “Miracle Worker,” accidentally slapped Eisenberg while filming one of their tussles. “But we kept doing the scene. As we continued on, I saw a red welt coming up on her face,” says Elliott. “When we finally finished, I said to Hallie, ‘I hit you! Why didn’t you break character?’ And she said, ‘The scene was going well!’ I was impressed. She’s the real thing.”