Continuity mistake: When Alex is giving Izzy her medication, he is holding a water bottle and an unpeeled banana In his right hand. Then the banana magically disappears and he is holding only the water bottle. Immediately, the banana reappears and it is now peeled. This all takes place in three quick shot which are from different takes.
Factual error: Derek performs CPR on Meredith in the back of the ambulance, but he does so incorrectly. He gives one breath and five compressions instead of two and thirty. Also, drowning victims need oxygen, and Derek should have used a BVM to ventilate Meredith, not mouth to mouth. Any doctor would have known how to provide proper treatment.
Continuity mistake: When Izzie is looking at the patient board, there are some lines on it which have been wiped out. But in the next scene we actually see Meredith walk to the board and wipe these exact same lines off (even though they were previously rubbed out...) (00:34:05)
Visible crew/equipment: When Burke and Cristina are walking along and Burke asks her if there is anything he should know about her religious holidays, you can see crewmembers, a boom and a stage light reflected in the glass running alongside. (00:05:30)
Continuity mistake: When Alex comes in to talk to Meredith who is sitting on the floor, Meredith has two files and there is another file sitting up on the table next to her. By the end of the talk Meredith now has all three files although she never reached up for the one on the table. (00:16:15 - 00:17:55)