USA can cobble together entire Law & Order: SVU marathons around celebrity guest stars. Even Taylor Swift has been rumored to be joining their ranks. But Swift would likely play an innocent victim. Or possibly a mean roommate who doesn't know where Jessica is...okay , she's not her keeper.Although Swift's character probably wouldn't wind up being be the perp, many celebs take on far creepier roles during their guest stints on SVU. They're the kind of characters that make you seriously consider switching the channel to something warmer and happier. Like C-SPAN. They are the unrepentant killers — those who, when presented with their crimes, laugh.These are roles some of your favorite actors have played, forever making reruns seem more than a little unsettling. But they're also impressive performances that landed more than one celeb a guest-star Emmy nomination.