I miss my own [name] and I mourn for everyone else's, because I'd like to love them, but I don't know who they are. (1.1.7)
R finds it impossible to love someone if he doesn't know their name. This is one of the reasons he falls for Julie so hard: she's the first person he's met in a long, long time who has a name.
I think I remember what love was like before. There were complex emotional and biological factors. [...] The new love is simpler. Easier. But small. (1.1.40)
Boy, yeah, love is complicated. R finds that without all the hormones and pheromones and pesky social things like talking or finding something in common, love is heck of a lot easier as a zombie. However, making it easy also kind of takes the fun out of it.
I want our cells to braid together like living thread. (1.2.40)
This is Perry's thought when he and Julie hook up for the first time. He has this desire to become one with her—which is another subtle foreshadowing, as at the end of the book Perry inside of R does end up combining cells with Julie (and vice-versa) to create something new.
I put a hand on my chest, over my heart. My "heart." Does that pitiful organ still represent anything? (1.6.50)
Can the heart still symbolize love even when it's not beating? More importantly, why does the heart even symbolize love in the first place? Doesn't that a fact that it's zombie chow kind of ruin that?
In my palm I can feel the echo of her pulse, standing in for the absence of mine. (1.7.66)
Just like R feeds off the brain of others to have memories, he kind of feeds off of Julie's love to have a love of his own. At least in this case, he isn't doing it literally, slurping Julie's veins out like spaghetti. Mmm. Spaghetti with red sauce.
I imagine [Julie] without skin. I know from grim experience that there is a beauty to her inner layers, too. (1.10.156)
So beauty isn't just skin deep, eh? R really loves who Julie is on the inside, quite literally, eh? Okay, we're out of jokes. This is just gross.
"Do you think it's stupid? [...] To fall in love." (2.1.53, 2.1.55)
This is a question Perry asks his dad, wondering if it's silly to fall in love when the end of the world is going on. Has this kid never seen a movie, like, ever? Love happens when you least expect it, kid, and it can happen at any time.
"If I kissed you, would I get... you know... converted?" (2.2.95)
Okay, while R believes that love runs more than skin deep, Julie is more of a looks kind of girl. If R looks like an extra from The Walking Dead, she probably wouldn't be eager to swap spit. Good thing he looks like this. Yeah, not too shabby for a dead guy.
I pull Julie into me and kiss her. (2.8.178)
That's right: "kiss her" not "eat her brain." So is the moral of Warm Bodies that a guy can change?
We smile, because this is how we save the world. (3.1.62)
And they're smiling because of love and passion. Not just heterosexual, borderline necrophiliac passion, but just a general passion for people, for laughter, for life.