At left, a You're A Good Man, Charlie Brown reunion with Kristen Chenoweth (a Tony winner for Sally in the musical revival) and Wrong Moutain's Ilana Levine (who played Lucy in Charlie Brown). At right, Sarah Jessica Parker and Wrong Moutain's leading man, Ron Rifkin. Wrong Mountain, an often savage look at the American theatre, concerns a bitter middle-aged poet who bets his ex-wife's new husband, a wildly successful Broadway playwright, he can write a smash play - and does. Mountain, by David Hirson of La Bete, performs at the Eugene O'Neill Theatre.