: 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.
: Meredith Grey remains largely sidelined in a hospital bed throughout the episode, a creative choice made to accommodate actress Ellen Pompeo’s real-life maternity leave; the character is written as having just donated a portion of her liver to her father. Production and Impact [S6E5] Invasion
: 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. : Callie Torres faces a personal crisis when
: 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. : In one of the show's most controversial
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:
: 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.
: 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".