Wonder Woman is coming to Smallville! Well, sorta. Lynda Carter, who played the DC Comics superheroine in the campy 1970s TV series, will appear in the April 12 episode of Smallville as Moira Sullivan, mother of intrepid Daily Planet reporter Chloe Sullivan (Allison Mack). The show placed Moira in a mental institution earlier this season, but all a network rep will spill about Moira's current status is that ''her whereabouts play a huge part in the episode.'' The rep will confirm, however, that Carter is set to appear in only a single episode.