Continuity mistake: When Christina is in the locker room eating a packet of crisps, everyone comes in and she asks them if they have any decent food. In the next shot you can see she is now holding an opened bar of chocolate. Then in the following shot we actually see Meredith hand her a wrapped bar, which Christina then opens (and the previously opened bar is gone, of course.)
Visible crew/equipment: In the NICU, when George starts boasting that he has the best quint, in the overhead wideshot we can see the T-mark (greenish yellow) on the floor near Kate, moments before Karev walks in and stands there. It's visible again just as Karev walks away.