Meredith is none too thrilled about the new girl Derek met at the bar. The fact that it's her sister can't help matters, either.
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Because Bailey is on the warpath? Because Mer and Der are hooking up in the on-call room and they want to watch? Who knows!
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Izzie has a new group of interns following her around. We will have to see how Dr. Stevens adjusts to being the one bossing peeps around instead of in the doghouse.
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Miranda tells Alex Karev who's boss around here. As if there were any doubt about that since his first days as an intern!
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Izzie and Alex used to be an item, but now they're just good friends. It's nice to see for fans of both characters.
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Rumor has it that Miranda Bailey is a little bit bitter and back to her bad-ass self in Season Four. Izzie Stevens could attest to this.
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Grey's Anatomy Season 4 Episode 1 Quotes

I tell you that I love you, and not one word? For 17 days? Where have you been?

Izzie

[narrating] In the practice of medicine, change is inevitable. New surgical techniques are created, procedures are updated, levels of expertise increase. Innovation is everything, nothing remains the same for long. We either adapt to change, or ... we get left behind.

Meredith