Alias fans weren't the only folks shocked by last Sunday's post-Super Bowl episode, which climaxed with the murder of Sydney's (Jennifer Garner) sweet roommate Francie (Merrin Dungey) at the hands of her never-before-seen evil double. Not even Dungey's closest friends knew the actress would soon transform into a femme fatale. Since October, she's been suffering under a vow of silence about the plot twist, and now she's dying to tell us all about it!

"J.J. [Abrams, the show's creator] said he'd send my character to Disney World, never to return, if I said anything," she tells TV Guide Online. "I've been holding this secret and living [like] Sydney Bristow... No one knew what was happening for so long. I'm breathing a sigh of relief and can't stop talking about it now!"

Dungey knew something had to change for her character, who'd been pushed to the sidelines to make way for the arrival of Syd's mother (Lena Olin). "I was getting frustrated because I'd come in once a week and say, 'Hey guys, do you want to try my soup, or bouillabaisse or brownies?'" she laughs. "I walked in my trailer, and I was like, 'If I see one more apron... Am I Florida on Good Times?'"

For months, Abrams and Dungey discussed different scenarios for the character, hoping to find a way to make the switch ring true. (Yeah, and we all know doppelgangers are quite a natural part of the real world.) Next thing the 31-year-old knew, she was training with world champion kickboxer Benny "the Jet" Urquidez, who's taught the likes of John Cusack, Jean-Claude Van Damme and David Lee Roth. "Jennifer is a badass... She is it," sasses the seasoned sitcom guest-star. "And if I'm going to have to get in there and tangle with her or any one of her fellow foes on the show, I've got to be ready."

Of course, before Dungey gets to threaten the free world with her deadly moves, she's got to keep up the best-friend act a little longer. "Even though some of the situations seem to be similar — me and Sydney in the house talking — you know Bad Francie is up to no good," she says with glee. "It's sooo good now. It is just delicious every time I get to jump into 'the Francinator.'"