Credit: \Danny Feld/ Getty Images Photo: Season 7: These Arms of Mine
From false-alarm lockdowns to abrupt resignations, here are the top OMG moments from this week's episode of Grey's Anatomy.

5. Alex sings Bieber

OMG — too funny. Alex feels bad for taking away little Lily's iPod for her scan, so he does her a solid and sings a Justin Bieber song over the intercom. (I mean, we think it's a Justin Bieber song. We're not fans ourselves, per se.) Plus, the technician in the booth with him gives him an are-you-crazy look.

4. Hospital lockdown
Ugh! Stupid, stupid Lexie. She got all impatient at the security checkpoint and tried raising a fuss, and then ran for it when that didn't work. But that just set off all the alarms and put the hospital into lockdown mode, trapping Jackson and his flatlining patient in a vestibule. And Lexie couldn't be publicly shamed for that?

3. Nicole tattoo
The whole grandiose arm transplant was almost scrubbed on account of a tiny tattoo? Really? I mean, we get the reasoning, but wouldn't they have sooner done a skin graft than call the whole thing off? It was OMG funny when Nora suggested changing her name to Nicole, but then OMG sad to hear the story behind the tattoo from Nicole herself.

2. Callie and Arizona quit
We had heard that Arizona would be headed to Africa (to accommodate actress Jessica Capshaw's maternity leave), but Callie is going with her? Callie gave up her prestigious position? That's true devotion, sure, but we're wondering how they will both be welcomed back into the fold later. They really quit?

1. Mary comatose
Wow. Grey's sure knows how to rip our heart out, stomp on it, and then put it back in our chest upside down. This was a doozy of a twist that a) helped make this episode the best of the season in our book and b) got us seriously verklempt. Poor Mandy Moore — we mean, poor Mary and Bill.