The Claire Colburn character in this movie (played by Kirsten Dunst) was the reason for "The A.V. Club" columnist Nathan Rabin's coinage of the term "The Manic Pixie Dream Girl," which later entered into common usage in movie writing. Rabin's definition of the term, which first appeared in a 2007 article titled "My Year Of Flops/The Bataan Death March of Whimsy Case File #1: Elizabethtown," was: "The Manic Pixie Dream Girl exists solely in the fevered imaginations of sensitive writer-directors to teach broodingly soulful young men to embrace life and its infinite mysteries and adventures. The Manic Pixie Dream Girl is an all-or-nothing-proposition. Audiences either want to marry her instantly (despite The Manic Pixie Dream Girl being, you know, a fictional character) or they want to commit grievous bodily harm against them and their immediate family. As for me, well, let's just say I'm not going to propose to Dunst's psychotically chipper waitress in the sky any time soon...(see Natalie Portman in Garden State for another prime example)."
When Drew and Claire are on the phone, he washes and hangs up his socks. A short while later he has the same socks on (yellow and white). Later, he is wearing green socks.
When Drew is on his trip planned by that Claire, we see a series of scenes suggesting that a lot of time passes. Drew browses through the book, changes CDs and from time to time takes a look at the father's urn. In these moments the book is opened always on the same page.
Towards the end of the movie, when Drew is driving, the camera shows a Wichita sign next to road. For a second, the very dirty top of the windshield (that the wipers can't reach) is visible. In the next shot, showing Drew from the side, the windshield is totally clean.