Who's More Doomed on Grey's: MerDer or Izzie?

Whoa. Mucho story progress on tonight's installment of Grey's Anatomy. Check out a sneak peek above of next week's episode (wherein Izzie and the robot fight for the future...), and then read on for a breakdown of what went down with Alex & Izzie, Sloan & Lexipedia, Callie & Arizona, Owen & Cristina, and, of course, Mer & Der...

Alex & Izzie: Aw, as the interns said, "The girl is toast." As correctly predicted by our commenter MDs, Izzie has "metastatic melanoma with mets (metastases) to liver, skin and brain"—and her prognosis, even with chemo and radiation, is supposed to be no more than a few months. Meanwhile, she's preternaturally calm and happy, enjoying her silly bickering friends and her boyfriend with a bright future, and doing an amazing job teaching her students. And Izzie's diagnosis and terminal illness is not just going to kill her—the consequences are going to be devastating to George and Alex, too. How are you handling it? Post in the comments.

Sloan & Lexipedia: As Marc put it, "You think you broke me, Little Grey? You're the one who put me back together!" They are ridic. Love them. Love. Also, Chyler Leigh does not look pregnant!

Callie & Arizona: Two words for you on this situation: Arizona = Yay! They have megachemistry, Callie is so darn winsome, and Arizona is the cutest little trick in shoe leather. More, please.

Owen & Cristina: It's awful that these two have to suffer, but if they didn't, they would be the odd men out in this world. Looking forward to Owen getting his head on straight, because Dr. and Mrs. Dr. McBadass have a lot to offer the world, not to mention this show. P.S.: Was Izzie's statement to Cristina before she revealed her cancer ("You're a robot. You can take it") overly harsh, or was it pitch-perfect for the characters and their relationship?

Mer & Der: Wow. Just wow. For an episode that started with Owen slamming Cristina into a wall, it was the end of the episode that was disturbingly violent. One of the creepiest things to appear on Grey's Anatomy since Rebecca/Ava's (Elizabeth Reaser) psychotic break was the moment when Derek swatted Mer's engagement ring across the meadow and then tossed the baseball bat at her. How are you feeling about their relationship right now? Mer is terribly believable when she says she's sticking with him, but how much can she (and we) be expected to take?!

Long story short: This episode was crazysauce with a side of nuts. Did you love it? Hate it? Post in the comments...