Will Smith has already made a star out of one of his children – son Jaden, 9, who costarred in 2006's The Pursuit of Happyness. Now, the acting bug has bitten again in the family.

Smith's daughter Willow, 7, makes her onscreen debut in his sci-fi thriller I Am Legend, due in theaters Dec. 14.

"She has a drive," Smith tells PEOPLE. "She has an energy and she just connects to human emotion. I think a big part was probably [seeing] Jaden after The Pursuit of Happyness. She saw what Jaden did, and she was like, 'I want that.'"

Still, there shouldn't be too much tension between the young Smiths. Smith says they have different styles – and goals.

"Jaden is [like] Johnny Depp," Smith says. "He just wants to do good work . . . He loves acting, he just wants to make good movies.

"And Willow is Paris Hilton," Smith says, laughing. "Willow wants to be on TV."

Smith says his daughter's strong personality contributes to her impressive work ethic. "You don't work with Willow," Smith says, teasing. "You work for Willow."

In one grueling outdoor sequence for I Am Legend, temperatures dropped well below zero, Smith says – but that didn't stop his daughter from finishing her scenes.

"Willow was out there and she has her stuff on and she's cold and she's getting a little irritable. And she looks at me and says, "Daddy, I don't care how low it goes. I'm going to finish.'

Continues Smith: "I was like, 'Wow, that's good baby, because Daddy's leaving if it goes any lower then that 1."

Another reason for the strong sense of professionalism: Will and Jada Smith make their children audition for their films. But when they told Willow she nabbed the role in I Am Legend, Smith says she turned to her brother, already a screen veteran, stuck out her tongue and teasingly taunted him.