Macaulay Culkin never had it so bad in ''Home Alone'': In Igby Goes Down, his little brother Kieran plays a Manhattan brat who gets stuck with a hateful, terminally ill mother (Susan Sarandon) and a schizophrenic father (Bill Pullman). First-time writer-director Burr Steers' acidulous satire doesn't go down easily, but a remarkable ensemble that also includes Ryan Phillippe as Igby's sociopathic brother redeems the movie, if not the characters. And Steers' mordantly quippy dialogue proves you can't spell ''dysfunctional'' without ''f-u-n.''

