The song playing while Cristina and Meredith were dancing it out (where does the good go) played in season 1 episode 4.
Fear (of the Unknown) is a song by Siouxsie and the Banshees.
When April Kepner is first shown treating a patient, she is conducting an initial exam, including checking her throat. April was notably fired in season six, after a patient in her care died following smoke inhalation, where her throat wasn't checked.