Cassandra Peterson has crossed paths with scores of aliens, monsters and other creatures as Elvira, Mistress of the Dark, but in this week's episode of Nickelodeon's CG Teenage Mutant Ninja Turtles animated series, the actress will voice a character that menaces mutants (and humans) for a change. This Friday, February 8 at 7 p.m. ET/PT in "The Alien Agenda," the Turtles will have to contend with "Mrs. Campbell," a nurse at April O'Neil's school with unfortunate ties to The Kraang. It turns out the mech-riding brains are none too pleased with April's latest school project and have sent an agent to deal with the budding scientist/martial artist. You can get a first look at the episode after the cut, although fans will have to wait until Friday to hear the Terminator-like Mrs. Campbell speak in Peterson's voice. Until then, we can all admire April's resourceful use of her school's mascot uniform in a fight.