As host of Sci Fi's guiltiest pleasure, Scare Tactics (which returns with new episodes Friday at 10 ET), Shannen Doherty is an accomplice to all manner of terrifying pranks. So she can't be entirely surprised by our first question: What would really freak her out?

"It would have to be something to do with water or sharks," she admits, perhaps foolishly, to TV Guide Online. "I'm petrified of sharks. Petrified. Like, I know I'm going to get eaten one day."

Aha! Now we've given the altered-reality prankathon's producers the info they need to spook their star. Yet for some reason, the Beverly Hills, 90210 and Charmed actress isn't quaking in her boots. What gives? "I don't think they'd do that to me," she says. "If you pulled a prank on me with a shark, I'd probably have a heart attack.

"That's like finding out somebody's worst fear and making it a reality," she continues, possibly trying to reassure herself that she won't soon be playing fish food in a small-screen remake of Jaws. "On our show, we do supernatural [stunts]. There are really sharks, but are there really aliens? That's the difference."

That being the case, Doherty doesn't feel the littlest bit of remorse for the big jolts that are given to her series' unwitting victims. "If I saw somebody react in a bad way at the end, then yes, I might feel bad," she offers. "But I've only seen people laugh and be like, 'Oh my God, that was the coolest thing ever!'

"As long as that's their reaction," she adds, "then we're doing our jobs." — with additional reporting by Michael Ausiello