You never know the biggest day of your life is going to be the biggest. The days you think are going to be big ones, they are never as big as you make them out to be in your head. It’s the regular days, the ones that start out normal. Those are the days that end up being the biggest. And today was the wedding. It was beautiful. Perfect. You never know the biggest day of your life is the biggest day, not until it’s happening. You don’t recognize the biggest day of your life, not until you’re right in the middle of it. The day you commit to something or someone. The day you get your heart broken. The day you meet your soul mate. The day you realize there’s not enough time because you wanna live forever. Those are the biggest days. The perfect days. You know, it was a beautiful day.

What a Difference a Day Makes is the twenty-second episode of the fifth season and the 100th overall episode of Grey's Anatomy.

Short SummaryEdit

The 100th episode! Meredith and Derek prepare for their wedding for later that day. Izzie starts to see Denny again, Arizona and Callie have relationship issues and Owen refuses to give up on George as a few graduation students are admitted.

Full SummaryEdit

While Izzie talks about how you never know big days are going to be big days, there are flashes of a wedding dress, the church, and the people gathered in the church, Izzie says today was the wedding. It was beautiful.

Derek and Meredith are standing in the church, that isn't decorated yet. They are getting married tonight, although Derek jokes they have nothing to do with the ceremony. They're just the bride and the groom.

Cristina wakes up Callie, who was sleeping on the couch in the residents' lounge. Cristina has to be a happy maid of honor tonight to get Meredith down the aisle. She's tired, because she had to sleep at the hospital since Callie wanted the apartment to herself to get freaky with roller skate girl. Callie explains they went to dinner, but she wasn't in the mood and she had to be here early to run the ER, anyway. Callie leaves as Meredith comes in. Cristina says it's the biggest day of her life, but Meredith doesn't want the peppy maid of honor thing. It's the biggest day of Izzie's life. Meredith is excited for the marriage, not the wedding.

Izzie herself is very excited. Derek gave her his credit card and told her to do what she had to do, so it's going to be perfect. Bailey says she's doing well, and Izzie agrees to that. It's wedding day and she's going. Bailey told her she could go. Alex and Bailey leave. Izzie scratches her head and notices her hair is starting to fall out. "You still look good," a voice says. She looks up and sees Denny. She knows what that means. He says he's sorry. She says she's still going to the wedding.

George asks Alex how Izzie is doing. Alex says he will worry about her. They ask Callie if she has something for them, but she says it's a slow day in the ER. George says she jinxed them by saying it, and the phone starts ringing seconds later. Callie picks up and yells there's incoming trauma.

Owen joins Cristina, who asks how things are going with his shrink. He says he's doing better, although it's slow progress. The ceiling fan above her bed was the trigger for the choking. His hand touches hers as she says they should probably get going.

The paramedics bring in several wounded teenagers. They were on their way to college graduation in an SUV that got hit. The teenagers ask about their friends. Callie asks the paramedics if they're all injured this badly, but the paramedic replies these are the healthy ones. Callie needs interns and Owen. One of the teenagers, David, goes into V-tach. George shocks him as the others beg to save him. 

Owen arrives in the ER and goes to take care of Becca. Alex tells her to stay calm. Becca says she has a speech to give. She's the valedictorian. All she's ever done is school. Today is the day her life is supposed to start, so she'd really like to live. Owen asks Alex to let him know the results of CT.

Owen goes to the other trauma room, where Jordan keeps asking about his girlfriend Dana. Cristina urges him to calm down so they can treat him. She promises to check on Dana when she can. Jordan says Dana is wearing a pink sweater.

Owen goes to check on George, who's taking care of a resuscitated David. George suspects he has cardiac contusions and Owen trusts him to handle it on his own. Lexie comes in with blood. David wants to know about Pete, who has red sneakers, and Michelle, who dyed her hair blue. Lexie will find them. David says today is for their families, and then codes.

Izzie has paged Derek to her room. After some wedding questions, including about his not-yet-written vows, she confesses she is seeing Denny again. That means another MRI.

Richard has a present from Derek for Meredith. He has to give it as Derek got pulled into something else. Meredith didn't know they were supposed to get each other presents and says their life together should be the present. She wants him to take it back. Richard says Derek got her a colectomy, her own first solo surgery. Richard will be overseeing it. He tells her happy wedding day and fills out her name on the board.

A stressed-out Callie is on the phone in the ER. Mark comes over and she tells him there are many digit amputations, nasty face lacs, and burns. Mark promises to stay around. The ER is getting flooded. Arizona comes over and asks what went wrong last night. They went out to the best restaurant in Seattle and then Callie ordered the salad, barely spoke, and then bolted. Callie claims she was exhausted and then gets up to tell people to move their patient to the hall.

George is performing CPR on David as Owen comes in to check. Lexie says he's been down for 20 minutes. George doesn't want to give up as David is graduating, but Owen says he's gone. Now he has to stop so he can save other people. Lexie calls time of death 9:24. 

Izzie is about to have her scan taken, but she's sure it's tumor. She tells Bailey that Denny is standing right behind her, and he confirms it's a tumor. He greets Bailey, and Izzie conveys the message. Bailey wants her to tell him to go home. She activates the scanner.

Becca is crying. She says she should have slept with David. She thought about it, but she would have fallen in love with him and she didn't want a relationship during school. Now David's dead. Owen comes in and Alex updates him. Owen tells Becca they're going to take her up to surgery soon.

Jordan is still worried about Dana, but Cristina says they haven't brought her in yet. She asks about his family. He says they're in Argentina, and he's supposed to fly out there tomorrow. His parents don't have the money to let him stay, so he has to go back. Dana called it D-day. He and Dana tried to break up, but they couldn't stay away from each other. Love is love, and it doesn't matter if you're not supposed to be together. Owen comes in to check. Jordan is stable enough for a CT. Jordan thinks maybe Dana got out in time, because she was gone when he turned around.

George is trying to stop a major bleed. Lexie realizes it's Pete as he has red sneakers. Lexie helps him dress the wound as he performs a pericardiocentesis for a pericardial effusion. While he's doing a second one, Pete flatlines. George asks for a cardio board, and then starts doing compressions. He refuses to lose another one.

Meredith and Richard enter the OR. He steps up to the table with her. She asks Bokhee for a scalpel. He compliments the way she asked for the scalpel. He peeks over her shoulder as she makes the incision.

Down in the ER, Mark talks to Callie about his toast, which doesn't bring up the future. He thinks that's good. Arizona comes over and says she couldn't have been that tired if she's working in the ER on her day off. Callie says she rallied. Arizona says she's lying. Callie claims she loves the ER. Arizona sighs and walks off. Mark advises her to tell Arizona.

George finds Owen and tells him his patients keep dying. He says he's in over his head. Owen won't pull him. Lexie sees Owen is working on Michelle, with the blue hair.

Derek, Bailey, and Izzie are looking at Izzie's scans, which are clear. Izzie says she really wants to go to the wedding. Then why would she tell them about Denny if there was no tumor? Denny is back, so that means something is there. Derek has an idea: if they could induce a hallucination, they might be able to pick it up on an EEG. Then they could see what part of the brain is hallucinating.

The paramedics bring in Dana, but she's D.O.A. as she lost half her blood volume. Cristina comes over and realizes who Dana is. As they're about to call it, Jordan appears and breaks down. While George calls time of death, the other doctors rush to aid Jordan, who's coding.

An angry Calle is on the phone, yelling they're closed to trauma. She hangs up as Arizona comes over again. She asks if Callie wants to just end things, because it seems that she can get enough of Arizona. Women are lining up for her, and Arizona can take it. Maybe this is just over. Callie says it is.

Meredith is doing fine. Mark comes in and asks how it's going. Meredith thinks it's going well, but he should probably ask the Chief. Richard agrees to that. Mark says coming up with a toast is a lot of work, so he hopes he won't have to be a best man a third time. It's his job to threaten Meredith. Richard's making sounds again, but claims everything's fine.

Bailey and Derek have set Izzie up for her EEG. Izzie confirms it's always Denny. She loved him, but she thinks she hallucinates him because she associates him with death. She is in love with Alex now, and she imagines her future with him. Izzie wonders what if she can't make him appear in time, as they have to be at the church in two hours. She will do her best so Derek won't be late.

Alex walks into the OR where Becca is about to be put under. She asks about her friends. She can take it. Alex deviates and asks her to hear her graduation speech. She worked hard on it, so she should do it. 

While she says that today is the day her life begins, David's body bag is zipped. Today, she becomes a citizen of the world. Today, she becomes a grown-up.

Today, she becomes accountable to someone other than herself and her parents.

Meanwhile, Meredith is still operating.

More body bags get closed.

Today, she becomes accountable for more than her grades. She becomes accountable to the world, to the future, to all the possibilities that life has to offer.

Meredith finishes up.

Izzie begs Denny to show up.

Dana's body bag gets zipped as well.

Today, Becca's job is to show up, wide-eyed, willing, and ready. She doesn't know for what.

Izzie keeps begging Denny.

Becca says she has to show up for anything, for everything. To take on life. To take on love.

In the ER, Cristina shocks Jordan again.

Meredith has closed the incision. Richard compliments her work.

Izzie asks Denny to show up now that she's asking him. He has to help her.

To take on the responsibility and possibility.

Cristina gives up. Owen takes her hand, but she walks out. Owen calls time of death 13:02.

Today, their lives begin. And Becca, for one, can't wait.

Izzie gets frustrated, but Derek sees something on the monitor. Denny has appeared next to Izzie and tells her he's here for her. Izzie is relieved that they found it, but then realizes what it means.

Derek and Bailey are looking at Izzie's scans. There's a very tiny tumor in Izzie's other temporal lobe. It was too small to pick up on a normal MRI. Bailey wonders how he can get to it when it's so small. Derek doesn't know what to say. He wishes there was something he could do for her. Izzie is one of the good ones. Bailey knows something he can do.

Arizona finds Callie sleeping on a gurney and she tells Callie she is hurt and angry. She thought they were going somewhere, but if Callie is just making the round of girl surgeons... Callie says they went to a fancy restaurant. The salad cost $26.95, and the wine $125 a bottle. Callie didn't even look at the entrees as she knew she couldn't order one because she was already out $75. Then the bill came and Arizona paid. Before they brought over the check, Callie was trying to figure out how to get through the rest of the week if her half was $75. She doesn't have 75 bucks because her father has disowned her and cleared out her bank account. Callie is working in the ER because she needs the money. 6 people died on her watch today and she's exhausted and fried. Callie wanted to stay in last night, but Arizona wanted to go out. Arizona says it's okay. They'll stay in and eat sandwiches. Arizona doesn't like sandwiches, but she likes the girl who has the sandwiches. Callie decides she likes pizza better, which also works for Arizona.

Meredith is done. Richard has been reading Ellis's journals, and he wishes she could be there today, for her first solo surgery. He says Ellis would have been thrilled, even though she wouldn't have been able to say it. Meredith thanks him.

Derek finds Meredith in the residents' lounge and she thanks Derek for her present. Now she has to get ready to put on the dress and walk down the aisle with people staring at her. Derek has an idea to make this day even better.

Owen compliments George's work today. The girl who survived was the one George didn't touch. Owen says he was able to help that girl because he had George on his team. Trauma is a team sport. You just have to go where you're needed.

Meredith sits down with Alex outside the hospital. She heard about Izzie's tumor. He's crying because he thinks Izzie's going to die. He asks if she doesn't have a wedding to get ready for. She says that's what she came to talk to him about.

Lexie takes care of Becca's central line. Becca sees she's crying.

A dressed-up Bailey is nervously waiting in Izzie's doorway. She's supposed to help Izzie get ready, but she's distracted. Meredith comes running in, holding her dress. This isn't her dress. Izzie thinks she's freaking out and speeches about how good marriage is. Bailey stresses that it's not Meredith's dress. Alex comes in wearing a tuxedo and says they're right. The dress is not for Meredith. They all smile at her.

Cristina and Meredith are putting flowers in Izzie's hair and removing her IV. She's sitting in a wheelchair at the church and wearing the wedding dress. Izzie doesn't even know how to begin to thank Meredith. She thanks her. Meredith asks who the maid of honor is. Izzie says Cristina, because Alex needs a best man and he was asking for Meredith. Cristina is not leftovers, though, because she tried to save Izzie's life. That makes her honorable.

Alex, Cristina, and Meredith are waiting at the altar as the doors open. Everyone in the audience stands up and turns around to look at Izzie. She starts walking down the aisle, but soon starts experiencing difficulties. She has to lean on a bench to stay up, but George steps in and takes her arm. He walks her down to the altar and he and Alex nod at each other.

The minister starts the ceremony.

It's time for the vows. Izzie didn't write anything, but Alex has something he wants to say. Today is the day his life begins. All his life, he's been just a smart-mouth kid. Today, he becomes a man. He becomes a husband. He becomes accountable to someone other than himself. Today, he becomes accountable to Izzie and their future, and all the possibilities their marriage has to offer. He'll be ready for whatever happens, for anything, for everything. To take on life, love, responsibility, and possibility. Today is the day their life begins. And he, for one, can't wait. Izzie says she loves him and kisses him, but the minister says not yet. He pronounces them husband and wife. They kiss as the audience applauds. Mark puts his arm around Lexie. Callie kisses Arizona. Cristina locks eyes with Owen, and Meredith and Derek smile at each other.

Alex helps Izzie to get back in bed. As he takes the flowers out of her hair, a chunk of hair follows. He says it's okay. She says it'll keep falling out. Alex says they'll shave it off, betting she looks good bald anyway. She starts crying. He tells her to stop. She's beautiful. He kisses her.

While Izzie's voiceover says you don't recognize the biggest day of your life until you're in the middle of it, Callie and Arizona are in bed, naked, eating pizza.

Cristina starts smashing on her ceiling fan with a hammer.

Izzie's voiceover mentions the day you met your soulmate as an example. Derek and Meredith have made a bed in front of the fireplace. She says it's the best non-wedding day ever. They're naked. He asks if she wants to go again. She laughs and kisses him.

Izzie says it's on that day that you realize you don't have enough time, as you want to live forever then. Those are the biggest, perfect days. It turns out she was talking to Denny, who bets she made a beautiful bride. She affirms it was a beautiful day. Alex comes in with a bottle of champagne and notices she put the scarf on. He told her she didn't need it as she looks gorgeous without it. Denny says he's right. Izzie tells him to go away as she wants to be alone with her husband. He disappears as Alex sits down on the bed. He takes the scarf off her head and kisses her on the forehead. He says his wife is hot. A bald Izzie laughs.


  • Meredith Grey
  • Cristina Yang
  • Izzie Stevens
  • Alex Karev
  • George O'Malley
  • Miranda Bailey
  • Richard Webber
  • Callie Torres
  • Mark Sloan
  • Lexie Grey
  • Owen Hunt
  • Derek Shepherd
  • Denny Duquette
  • Arizona Robbins
  • Becca Wells
  • Jordan
  • David
  • Interns Dani, Steve, Claire, Pierce Halley, and Leo Byrider
  • Minister (left)
  • Dr. Knox
  • Paramedic #1
  • Paramedic #2
  • Paramedic #3
  • Paramedic #4 (right)

Main CastEdit

Special Guest StarEdit

Guest StarsEdit



  • Jennifer Couch as Dana

Medical NotesEdit

Izzie StevensEdit

  • Diagnosis:
    • Stage IV metastatic melanoma
    • Brain tumor
  • Treatment:

Izzie was still in the hospital for her cancer treatment. She was off the IL-2 and her incisions from surgery had healed well, but her hair started to fall out and she started seeing Denny again, meaning she had another brain met. Derek ordered another MRI to find it so he could remove it. The MRI didn't show anything, so they planned to use brain mapping to find the tumor. It worked and Derek located the tumor. It was very small and Derek didn't believe he'd be able to remove it.

Owen HuntEdit

  • Diagnosis:
    • PTSD
  • Treatment:
    • Talk therapy

Owen told Cristina that things were going well with his shrink.

David SimonsEdit

  • Diagnosis:
    • Chest contusions
    • Cardiac contusion
  • Treatment:

David, 22, came into the ER after the SUV he was driving was hit by a semi. He had chest contusions, but his vitals were stable. In the ER, he coded and they were able to resuscitate him. Despite that, he had multiple arrythmias, so George suspected cardiac contusion. He coded again. George put in a chest tube, but there was no blood. George tried CPR for 20 minutes before Owen told him it was over. He was pronounced dead at 9:24.

Becca WellsEdit

  • Diagnosis:
    • Stomach herniation
    • Lacerated diaphragm
  • Treatment:
    • Central line
    • Surgery

Becca, 21, was brought to the ER after the SUV she was in was hit by a semi. She had some shortness of breath, but no hemothorax or pneumothorax, so they sent her for a CT and some x-rays. Her scans revealed a herniating stomach and a laceration on her diaphragm. She was told she'd be having surgery soon. At the end of the day, she was stable.


  • Diagnosis:
  • Treatment:

Jordan, 22, was brought to the ER after the SUV he was in was hit by a semi. He was stable and was ready to be taken to CT. When he saw his girlfriend, Dana, dead, he coded and was unable to be resuscitated. He was pronounced dead at 13:02.

Derek's PatientEdit

  • Diagnosis:
  • Treatment:
    • Craniotomy

Derek told Izzie that he had a craniotomy to get to.

Meredith's PatientEdit

  • Diagnosis:
  • Treatment:
    • Colectomy

As her wedding present, Meredith got her first solo surgery, a colectomy. The surgery went well.

Arizona's PatientsEdit

  • Diagnosis:
  • Treatment:

Arizona mentioned having four back-to-back surgeries and a kid on life support.


  • Diagnosis:
    • Chest wound
    • Pericardial effusion
  • Treatment:

Pete was brought into the ER after the SUV he was in was hit by a semi. He had a severe chest wound and pericardial effusion. George tried to remove all the blood, but he was unable to resuscitate and Pete was pronounced dead in the ER.


  • Diagnosis:
  • Treatment:

Michelle was brought into the ER after the SUV she was in was hit by a semi.


  • Diagnosis:
  • Treatment:

Dana was brought to the ER after the SUV she was in was hit by a semi. She was pronounced dead on arrival at 10:45.


Song Performer Scene
"First In Line" Matthew Mayfield
  • Derek and Bailey give Izzie an EEG and wait for her to see Denny.
  • Becca asks about her friends. Alex asks to hear her graduation speech. She gives her speech.
  • The five college kids they've lost are zipped into body bags.
  • Meredith performs her solo surgery.
  • Cristina unsuccessfully tries to revive her patient.
  • Owen calls time of death.
  • Denny finally appears to Izzie.
"Another Likely Story" Au Revoir Simone
  • Arizona and Callie agree to get pizza on their next date.
  • Richard congratulates Meredith on her surgery and they talk about Ellis.
  • Meredith thanks Derek for his present, and he pitches his idea to Meredith.
  • Owen tells George he did well today.
"Turn to Stone" Ingrid Michaelson
  • Izzie gets ready for her wedding and chooses Cristina as her maid of honor.
  • Izzie walks down the aisle, with help from George.
  • The minister performs the ceremony.
  • Alex uses Becca's speech as his vows.
  • Alex and Izzie share a kiss as their guests applaud.
  • Alex helps Izzie to get back in her bed at the hospital.

Notes and TriviaEdit

Grey' s Anatomy 5x22 The 100th Episode Promo

Grey' s Anatomy 5x22 The 100th Episode Promo


Episode StillsEdit

Behind the ScenesEdit

100th Episode CelebrationEdit


Meredith: Just a normal day.
Derek: Normal day. Going to work.
Meredith: Just a normal day, that ends in a ceremony in a churchy church.
Derek: This has nothing to do with us, we're just the bride and groom.

Callie: No! We are closed to trauma! Because we have trauma coming out of our butts! Oh, well have a nice day to you too! [sees Arizona] Oh, for the love of...
Arizona: So the ER is fun, but I'm not. You can get enough of me? Is that what you are saying? I mean, do you just want to just end this? Because there are women that are lining up for me. I'm hot.

Minister: Dearly beloved. We are gathered here today to celebrate the wedding of Alexander Michael Karev and Isobel Katherine Stevens. This is a sacred right. An ancient right. As Isobel and Alex prepare to join their lives, it is important to understand that everyone present has played a part in shaping their lives. And, will continue to play a vital role in their continuing future. And thus, we are here not only to witness their vows to each other, but to bestow upon them our blessing. And, now the couple will read their vows.
Izzie: Oh, we didn't write anything.
Alex: No, wait. I have something I wanna say. Today's the day my life begins. All my life I've been just me. Just a smart mouth kid. Today I become a man. Today I become a husband. Today I become accountable to someone other than myself. Today I become accountable to you. To our future. To all the possibilities that a marriage has to offer. Together, no matter what happens, I'll be ready. For anything. For everything. To take on life, to take on love. To take on possibility and responsibility. Today Izzie Stevens, our life together begins. And I for one can't wait.
Izzie: I love you. (kisses him)
Minister: Ahem, not yet!
Alex: Hurry up!
Minister: By the power vested in me, by god and the state of Washington, I now pronounce you husband and wife.
Izzie: Now?
Minister: Now.
(Izzie and Alex kiss.)

Becca: How are my friends doing? Just tell me. I can take it. I mean, I can't... but I can. Did someone else die?
Alex: Why don't you tell me your speech? Your graduation speech.
Becca: I can take it.
Alex: Becca, just... just give me your speech. You worked hard on it. So, you should do it. Right now. Come on.
Becca: Today's the day my life begins. Today I become a citizen of the world. Today I become a grown up. Today I become accountable to someone other than myself and my parents. Accountable for more than my grades. Today, I become accountable to the world. To the future. To all the possibilities that life has to offer. Starting today, my job is to show up wide eyed and willing and ready. For what, I don't know. For anything. For everything. To take on life. To take on love. To take on the responsibility and possibility. Today, my friends, our lives begin. And, I for one can't wait.

See AlsoEdit

A complete overview of this episode's crew can be found here.

The Grey Matter blog post on this episode can be found here.