Invasion - [s6e5]

: Fans often remember this episode for the "dark and twisty" bonding between Cristina Yang and Alex Karev, both of whom seek solace in Meredith's room as they deal with the fallout of the merger.

: In one of the show's most controversial turns, Izzie makes a critical medical error during a dialysis treatment that puts a patient's life at risk. Due to the hospital's budget cuts and her mistake, Chief Webber fires her, leading her to leave Alex Karev with nothing but a letter. [S6E5] Invasion

: The episode was written by Mark Wilding and directed by Tony Phelan . : Fans often remember this episode for the

: This episode served as the first half of a crossover event with the spin-off Private Practice . The storyline of the patient Izzie endangered, Sarah Freemont, concludes in the Private Practice episode "Right Here, Right Now". : The episode was written by Mark Wilding

The "invasion" refers to the arrival of residents from Mercy West, including , Jackson Avery , Reed Adamson , and Charles Percy . The episode portrays a literal battle for space and patients:

: Callie Torres faces a personal crisis when her father, Carlos, returns to the hospital with a priest in a misguided attempt to "cure" her bisexuality.

: Seattle Grace residents are forced to compete for surgeries and equipment with their new rivals. Tensions boil over when Reed Adamson attempts to take George O'Malley's old locker, leading to a confrontation with Izzie Stevens.