The song playing while Cristina and Meredith were dancing it out "Where Does the Good Go" played in No Man's Land (2005).
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.
Cristina says she has to go to the mall to get a European phone charger, but she was just in Zurich using her phone a few weeks earlier. It's unclear why she would need a new one when she presumably had one before.
