03/23/2012 at 08:00 AM EDT
plays the Evil Queen
in the new Snow White film Mirror, Mirror
, but it turns out the Oscar winner has some tricks up her sleeve even in her own house – especially when it comes to her kids.
Roberts, 44, says she gets a huge kick out of scaring her children
– Henry, 4, and 7-year-old twins, Hazel and Phinnaeus.
"If I hear them coming and they don't know where I am in the house, I crouch down in their private space and [when] they come in, I jump out," she tells Ellen DeGeneres
on Friday's The Ellen DeGeneres Show
. "Really, little people can just catch air. They just vault."
Still, despite her antics at home, Roberts says her kids were only allowed on the set at certain times, given her character's less than hospitable demeanor
"They were never there when I was talking, because I only say wretched things," she admits.
Roberts also got a taste of her own medicine during her appearance on the talk show. Before the taping, DeGeneres hid in Roberts's private bathroom and jumped out when Roberts walked in. Later, in front of the audience, a man in a Snow White costume snuck up behind Roberts, prompting her to shriek.
"You said, 'Now I know how my kids feel,' " DeGeneres said.
But it seems the actress may have learned her lesson even before Ellen turned the tables on her.
"I realized I was getting too much joy from it, so I've had to tone it down," she says about spooking her kids. "It's so wrong. It's like child abuse."