Casting: Eric Dane (Mark Sloan) doesn't appear in this episode.
Ratings: 13.79 Million Viewers
Trivia: We learn in this episode that Callie's father's name is Carlos.
Meredith (opening voiceover): When you get sick, it starts off with a single infection. One lone nasty intruder. Pretty soon the intruder duplicates. Becomes two. Then those two become four. And those four become eight. Then, before your body knows it, it's under attack. It's an invasion. The question for a doctor is, once the invaders have landed, once they've taken over your body, how the hell do you get rid of them?
Meredith: Hey, we are not some stupid hosts, they can't invade us. They can't attach themselves to our faces, then while we're eating spagetti explode out of our chests and skidder across the floor. This is our ship, this is our ship.
Lexie: Excuse me, our you quoting that Sigourney Weaver movie?
Meredith: Shut up.
Izzie: That's what happens when you live here. You watch a lot of TV.
Meredith: We own this hospital. We were born in this hospital, and we will hold this hospital with our last gasping breath.
Mr. Torres: I don't know you well enough to talk about her. We're not gonna do that.
Arizona: Most people think that I was named for the state, but it's not true. I was named for a battleship, the U.S.S. Arizona. My grandfather was serving on the Arizona when the Japanese bombed Pearl Harbor, and he saved 19 men before he drowned. Pretty much everything my father did his whole life was about honoring that sacrifice. I was raised to be a good man in a storm, raised to love my country, love my family and protect the things I love. When my father,Colonel Daniel Robbins of the United States Marine Corps, heard that I was a lesbian, he said he only had one question. I was prepared for "how fast can you get the hell out of my house?" But instead, It was "Are you still who I raised you to be?" My father believes in country the way that you believe in God. And my father is not a man who bends, but he bent for me because I'm his daughter. I'm a good man in a storm. I love your daughter, and I protect the things I love. Not that I need to. She doesn't need it. She's strong and caring and honorable. And she's who you raised her to be.
Mr. Torres: Leviticus: Thou shalt not lie with a man as one lies with a female. It is an abomination.
Callie: Oh, don't do that, Daddy. Don't quote the Bible at me.
Mr. Torres: The outcry of Sodom and Gomorrah is great, and their sin is exceedingly grave.
Callie: Jesus: A new commandment that I give unto you, that you love one another.
Mr. Torres: Romans: But we know that --
Callie: Jesus: He who is without sin among you, let him cast the first stone.
Mr. Torres: So you admit it's a sin --
Callie: Blessed are the merciful for they shall obtain mercy. Jesus: Blessed are the pure in heart for they shall see God. Jesus: Blessed are those who have been persecuted for righteousness sake for theirs is the kingdom of heaven. Jesus is my savior, Daddy, not you! And Jesus would be ashamed of you for judging me. He would be ashamed of you for turning your back on me. He would be ashamed.
Meredith (closing voiceover): What do you do when the infection hits you, when it takes over? Do you do what you're supposed to and take your medicine? Or do you learn to live with the thing and hope someday it goes away? Or do you just give up entirely and let it kill you?
Episode Title: Invasion
"Invasion" is the title of a song by several artists including Eminem, Ashley Roberts, and Lil Wayne.
It Happened One Night: When Christina goes into Meredith's room, Meredith is crying and watching the 1934 black and white film It Happened One Night.
Aliens: When Meredith is complaining about the Mercy West employees invading Seattle Grace she quotes lines from the 1986 James Cameron film Aliens.