Anna Faris is famous for taking on different roles on TV and in movies, but as part of Klondike’s campaign, she’s trying something new.

“I go undercover in different characters and try to manipulate people in different situations,” says Faris of the campaign, which relaunched its signature slogan, “What would you do for a Klondike bar,” by asking unsuspecting strangers what they would do for the iconic ice cream.

“I’m thrilled to be working with [Klondike],” she tells PEOPLE. “But I have to tell you, it’s been a bit terrifying. I think people think that actors are good liars, but maybe I’m not a good actor or a good liar!”

Off camera these days, Faris has her hands full with 6-year-old Jack, her son with ex-husband Chris Pratt.

“He loves making traps,” she says. “He’ll put ropes up so I trip over them, which annoyingly I seem to fall for all the time.”

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Hijinks aside, “Six is such a perfect age,” gushes Faris, 42. “He wants to be independent, he wants to be cool, but he’s still that snuggly kid.”

Adds Faris: “He crawls into bed with me every night. It’s so sweet. It’s that precious time that I know is going to [eventually] disappear.”