One of the better things about a good episode of NBC's stalwart Law & Order: Special Victims Unit is that you can rarely tell where it's headed. Is tonight's cameo-heavy hour (10/9c) the latest condemnation of reality TV's sordid excesses? Sure looks that way at the start, as we encounter an especially slimy Michael McKean (relishing his repulsiveness) as the predatory producer of a crap-tastic train wreck titled Showgirls, featuring young hopefuls who would do "whatever it takes" to land the starring role in a Broadway musical. (No small irony this is airing the week of the all-important-to-NBC Smash premiere, where such things could never happen!) As he liquors up a nervous contestant for her "audition," he leers for her to "seduce the audience. Let them know you want this." Doesn't take a genius to know where this is going.