The episode's central plot twist occurs when Meredith and Derek decide to give their meticulously planned wedding to Izzie and Alex.
In , the Season 5, Episode 22 milestone titled " What a Difference a Day Makes " is a landmark 100th episode that originally aired on May 7, 2009. It is widely celebrated for its emotional depth, shifting from a planned grand wedding for Meredith and Derek to a poignant ceremony for Izzie Stevens and Alex Karev. The Unexpected Wedding [S5E22] What a Difference a Day Makes
: Rhimes described the episode as the moment Meredith evolved from a "dark and twisty" girl into an "extraordinary" woman capable of choosing happiness. The episode's central plot twist occurs when Meredith
: George O'Malley faces an emotional crisis when almost all the students from the accident die under his care, leaving him devastated until Owen Hunt helps him see the lives he did save. The Unexpected Wedding : Rhimes described the episode
: As a wedding gift, Derek gives Meredith her first solo surgery—a successful colon surgery overseen by Richard Webber.
: To promote the 100th episode, ABC created a real wedding website for Meredith and Derek that fans could actually visit and RSVP to.