When Larry and Kate discover a bag of catnip in Sierra's room they fear the worst -- that their teenage daughter has become a ""nip-head."" Taking the advice of the community drug counselor, they decide to confront Sierra but only cause her to run away. Meanwhile, in their quest to experience the ""ah"" they observed in a recent 7-Eleven TV commercial, Siegfried and Roy venture to the local convenience store to claim the ultimate prize -- ""The Big Gulp.""