A busload of fume-sickened school kids...a gunman whose shooting spree claimed 19 victims...a guy in an opossum outfit who bit a man dressed as a kangaroo. They and so many others all converge at ER. The gurneys keep rolling in a superlative Season 7 that includes Abby's reunion with her mother, a turbulent woman who suffers from bipolar disorder. Also making the rounds in the 22 episodes: Carter returns from detox, Abby goes back to square...