Meredith: (opening voiceover) Before we were doctors, we were med students, which meant we spend a lot of time studying chemistry. Organic chemistry, biochemistry. We learned it all. But when you are talking about human chemistry, only one thing matters -- either you've got it or you don’t.
Derek: What's new with you?
Meredith: I saw my half-sister half naked.
Cristina: I am painting Burke's apartment so I can stop calling it Burke's apartment. A happy color. Red. Like blood.
Izzie: I love George. Oh, God I do, I love him, and I'm so happy because he's kind and smart and um, sweet and sexy. He's perfect, perfect, except for the fact that he kisses like a chicken. You know a chicken pecking the ground for food, justs pecking and pecking and pecking, and when he's pecking at me like that I forget that I love him, I forget that he's kind and sweet and sexy and I just wanna scream, "Stop pecking at me!" Did he peck you like a chicken, Mer?
Derek: Oh, I'm late. Dropped off the Chief's dry cleaning.
Mark: You're doing his laundry?
Derek: I'm helping out.
Mark: Yeah, what's he doing?
Derek: He has an extensive DVD collection.
Mark: You're dating the Chief. Huh.
Meredith: You look weird.
George: I don't look weird.
Meredith: What's wrong?
George: I look fine.
Meredith: I know you.
George: It's horrible. The sex. With Izzie... horrible. It's like she's trying to hard it's...you ever seen a porno? Not that Izzie's a porno; she's an angel, but it's like she's trying to...channel a porn star and she's trying to act all dirty and sexy, which sounds great, right? But in reality I just wanna say, "Izzie, just because you can do that with your legs doesn't mean that you should."
Meredith: Uh...I wanna run.
George: Run, run. Run now!
George: You know, he did this so his parents will get a divorce. He made himself sick so that they would take hi seriously.
Bailey: Mmm. I bet they take him seriously now.
George: Nah. They just said that they would try not to fight as much.
Bailey: I am elbow deep in their eight year-old. Sounds like somethin' a little extra effort can't fix.
George: You're probably right.
Bailey: I am so right. About so many things, it'll make your head spin.
Meredith: (closing voiceover) Chemistry, either you've got it. Or you don't.
When Bailey is performing surgery on Brian she says that there are "seven magnets in the tray" and she needs to find one more (because George says he swallowed eight). However, George only discovered that they were magnets when Ryan spat up a cluster of them. Brian could not have swallowed eight, spat five up, and still have eight in his body.
Sloan's face lift patient is able to talk and move their face freely after surgery. Usually a face lift patient is too sore to move their face so much for days and weeks afterwards.
When Bailey is pulling the magnets out of the boy during surgery they are not sticking together in the surgical tray like should be. They are magnetic and should be stuck to one another and to the metal of the tray.
When Izzie goes to check on her post-op patient Harriet, her hair changes between a loose bun and a ponytail with a headband several times.
Cristina can be heard saying "Get me a crash car, she's not breathing," during the Grey's Anatomy title sequence. However, before the screen fades to the title you can see there is already a crash cart there.
When George's patient returns to the clinic claiming to have eaten 8 more marbles, they fall through his armpit and not his mouth as he bends over to regurgitate them.
Episode Title: Physical Attraction, Chemical Reaction
"Physical Attraction, Chemical Reaction" is the title of a song by Madonna.
The Godfather: Richard Webber quotes a line to Derek, saying "I am going to make him an offer he can't refuse."
This is a very famous line from the 1972 film The Godfather.