Sylar: Forbidden fruit. My favorite kind.

Tracy: I can get a latte here, no problem, right?
Noah: I saw a cow about a mile back get some espresso, we're in business.

Claire: You awake?
Gretchen Berg: Yeah. You?
Claire: Yep.
Gretchen Berg: Are you afraid I'm gonna kiss-attack you in your sleep?
Claire: Maybe.

Gretchen Berg: Look at us. All tied up in the dark.
Claire: You know, they have entire websites devoted to this.

Matt: You can't control me. You've never been able to do that.
Sylar: Well, I had a compelling reason. Let's face it, your wife is kinda hot.
Matt: Enough!
Sylar: That is the second Parkman I've made scream today.

Deputy Gill: "I feel the darkness surrounding me. I am the bringer of death."
Noah: He's 17 years old. Half the songs in his iPod sound just like that.
Deputy Gill: Well, maybe I should read you the part about killing animals.

Gretchen Berg: Wow! We couldn't be more different. Maybe we're strange attractors.
Claire: Strange attractors?
Gretchen Berg: It's a physics thing. Everything in the universe has a magnetic charge, right? So strange attractors are particles that end up together that don't really belong together, but when they're together they're super-powerful, Sort of like we could be? Or not.

Tessa: You don't have to go all Buffy on us!

Buffy the Vampire Slayer was a character created by Joss Whedon, a cheerleader/preppie type who happened to have an inherent talent for slaying vampires, and, with enhanced reflexes and natural combat instincts, was a match for any vampire -- It is a particularly appropriate reference for Claire, who was a former cheerleader.

Sylar: Forbidden fruit. My favorite kind.

Sylar says this in Matt's head at the beginning of the episode, but it alludes in two ways to the end of the episode. In addition to Matt grabbing an apple as he walks away from his wife to go take a shower (after which it is revealed that Sylar's mind has taken full control over Matt's body), it is also an allusion to the apple itself, which is often identified (without adequate justification) as the "forbidden fruit" in the Garden of Eden, the eating of which became Original Sin, and resulted in Adam and Eve being ejected from the Garden.

Gretchen's description of a "strange attractors" seems to be some kind of an amalgam between the strange quality assigned to quarks, and the concept of magnetic attractors. Her description is utterly incorrect. The term "strange attractor" refers to a special type of non-repetitive pattern between two objects (think of an "orbit", which is a special case, but less predictable), first developed in the course of what is called Chaos Theory.