As Derek talks about the Alzheimer's clinical trial over breakfast at home, Alex gives Meredith a sidelong glance.
Callie and Arizona sit down with their parents for dinner. Mark is there and proposes a toast. Callie's dad is puzzled about Arizona's dad being known as 'The Colonel'. The awkwardness continues when he tries to show he's okay with them being gay by talking about a pride parade.
At the hospital, the residents watch Alex present his African orphan results. Webber tells them to keep it down. After, Webber takes Jackson to clean his mouse cages. Jackson complains to Lexie, who is certain he'll get approval to work on humans any day now. Jackson notices one of the mice seems dead.
Derek and Alex see to an African baby girl named Zola. Derek orders an MRI. When the test results come back, Derek tells Alex to book an OR. Alex gets Meredith alone and warns that he saw her messing with the blind trial. She denies doing anything wrong. When Alex goes into surgery with Derek, he tells him he was right about Meredith being the best choice for the Alzheimer's trial.
Arizona, Lexie, Christina and Teddy are with a young boy from Africa, who asks them to wait to tell his family back home if he dies - he doesn't want to ruin his sister's birthday. Arizona reassures him and they look at his chest - they see his heart beating through a thin layer of skin!
Christina is assisting Owen and complains that Teddy won't let her do anything. He suggests she apologize. Stark joins Owen to look at a young African girl's x-ray - she has AIDS. April tries to tell the girl they will help her in her language. Stark mocks her. Christina finds Teddy in the elevator and apologizes for going over her head. Teddy questions her motives, then goes to discuss it with Owen, who tells her she should put Christina back on her service. Teddy argues that Christina hasn't learned anything. April catches up with Stark and they argue about the young girl. She thinks he's treating her differently, but he denies it. The young girl suffers a crisis, so they rush her into the OR.
Arizona meets Callie and the parents for a quick wedding rehearsal. As they're getting in their spots, Mark enters and inadvertently takes the Colonel's position. Callie's dad calls him over, but warns him not to call him his father-in-law. Callie's mother excuses herself. Arizona and Callie take a moment alone to stress about their parents. They smile about getting married and giggle. Callie goes to show her mother her dress and gets a muted reaction. Her mother speaks out about her marrying a woman and having a child out of wedlock - she tells her she will not go to heaven. Her mother says she can't be here - it isn't right. Callie's father apologizes. She says he has to go with her mother.
Back at the hospital, the brother of the African boy with the heart problem is despondent. She sits with him. Stark bugs April about not answering pages. She tersely explains that she's making food for the young girl.
At home, Meredith can't get a response from Alex, who says he's keeping his mouth shut. She says she didn't change anything, but he guesses correctly that she did a switch. She asks if he's going to tell. Derek enters and Alex leaves.
At Callie's place, Mark tells them that their pastor's wife had an accident and won't be able to make it to the wedding. Callie is frustrated - it was very difficult to find someone willing to marry them. She huffs to just forget it. Later, Bailey shows up and Callie breaks down, mocking her attempt at a wedding. Bailey says she doesn't need her mother, and the service can be anywhere. She tells her if she's willing to commit herself to another human being - that's real.
At the hospital, Jackson shows Webber the MRI on his mouse. He proves something, and they are ecstatic to bring the mouse back to life. Arizona, Mark, Christina, and Teddy do a surgery. Teddy doesn't let Christina do anything. Stark corners Owen and tells him he would like to recommend April Kepner as Chief Resident - she goes above and beyond for her patients.
Meredith arrives at work, where Derek calls her in to meet Zola. He asks the nurse to excuse them, and then tells her, "Let's adopt this baby." Meredith is stunned. He says he can't imagine her being with any other family - and she needs one. Later, they look at all the adoption paperwork, and Derek says they'll take it one step at a time.
Mark, in a suit, arrives to get Arizona, who is crying about missing her brother. He holds her.
Derek and Meredith arrive at city hall. He asks if she's ready. She is. He says, "Let's get married." Their names are called and the ceremony begins. They didn't have time for rings, but sign the papers and are pronounced man and wife. They go straight back to the hospital to see Zola.
Bailey walks up the aisle nervously. Mark reassures her. Music plays and Arizona comes up the aisle on The Colonel's arm. Mark then walks Callie up to the altar and gives her away. Bailey begins the ceremony to marry them. They exchange vows and rings. Bailey pronounces them wife and wife.
Callie and Arizona dance at their reception as April takes photos manically. Owen, Christina, Alex, Jackson, and Lexie look on. Talk turns to the Chief Resident position. Owen says Stark recommended Kepner. Webber takes Christina aside and says he thought she'd be front-runner. Christina corners Teddy and attacks her about her ego ruining her chance for Chief Resident. Teddy says she still doesn't get it and joins her date - Andrew Perkins. He asks her to come with him to Germany - he wants to start a life with her. When the father/daughter dance is announced, Mark fills in with Callie, but her real father appears - he turned the car around. Callie beams.
Spoilers for Next Week:
The race for Chief Resident heats up.
Christina tells Owen no sex.
Webber admits he has a 'thing' for the underdog.
The race for Chief Resident is starting to wear on me - I don't really see any of them as being ready. I love Derek's spontaneous suggestion to adopt the beautiful baby girl, and the ensuing surprise marriage, but dread Meredith's actions in the clinical trial coming back to haunt her. I love that Callie's dad, who was once dead set against her same sex relationship, was the one who wound up being the most accepting and coming through for her. I also enjoyed the moments between Mark and Arizona, and Bailey and Callie. I'm not sure what to make of the battle between Christina and Teddy, but think they need to meet halfway - Christina is so often her own worst enemy. Stark recommending April for Chief Resident was the nicest thing I've seen him do - who knew?!