When Meredith and Cristina are talking in the bar you can hear them say the exact same words from the pilot episode.
Most of the songs featured in this episode were also featured in the Pilot episode.
When Cristina spilled the secret of Alex and April having a secret affair behind's Meredith's back, in exasperation Charles says "Ah, shoot me now!" which is ironically how he died when the shooter was in the hospital.
The staff are wearing different scrubs, the female doctors' scrubs are more form fitting which may be a result of having a female chief rather than a male chief.
In the conference room sequence at the beginning, Ellis Grey is wearing a lab coat that says Chief of Surgery. The room they walk into has a sign that says Chief of Staff