As a writer, I don't think there's anything more difficult than characterization. It's easy to find yourself swimming through murky water when attempting to morph an unlikable character into a vulnerable, likable one (think Jack Nicholson in As Good as It Gets), you have to hit all the right notes to get your audience to actually feel sympathetic for this person who makes it so hard to love him. And in the case of Michael Cera, sometimes it's even harder just to maintain a consistent personality, such as he did, in portraying Oh, a Gatherer (as in Hunters and Gatherers) in Year One. His soft voice, slouched posture, controlled facial expressions, and perfect comedic timing, all helped to make his character believable in an utterly ridiculous, unbelievable movie. In fact, I was so engrossed in this movie, that when I went to check on the brownies I was baking, I didn't stop and think, hmm, they're still soupy looking after 20 minutes -yeah, the oven wasn't on. But my point is that, Michael Cera's consistency of character made me, as the viewer, feel a familiarity with his speech, actions, thoughts, mannerisms...traits, essentially, that I could almost predict what he would say or do in the next scene. That's what good writing is, connecting your readers to your characters so that they feel a bond with them like they're real people.
So thanks, Michael Cera. And if you want a good laugh, go rent Year One ~