“Saturday Night Live” began its first show after Friday’s Sandy Hook Elementary school massacre in Connecticut with a children’s choir singing “Silent Night.” “SNL” paid its respects to the victims and survivors of the tragedy by having youngsters from the New York City Children’s Chorus perform as the episode opened, instead of using one of its traditional comedy monologues by the guest host. Guest host Martin Short appeared as planned later in the episode, which also featured a comic sketch about Kate Middleton’s obstetrician and a surprise guest appearances by former “SNL” cast members Kristen Wiig, Jimmy Fallon and Tina Fey, actors Alec Baldwin and Samuel L. Jackson. Paul McCartney served as the musical guest. McCartney and the surviving members of Nirvana once again united to perform their new collaboration, “Cut Me Some Slack,” three days after unveiling the collaboration at the “12-12-12: The Concert For Sandy Relief.”