Okay, I simply love this moment in Attack on Titan. Petra comes in to talk to Eren after Levi leaves the room, seeing what she believes is a look of disappointment on Eren’s face. She assumes it’s because Levi isn’t the grand, perfect, hero everyone expects him to be. He isn’t a Captain America or a, well, Erwin Smith. He doesn’t have the massive build of Erwin or Mike, he’s uncouth, and he’s far from welcoming and constantly speaking of the glory of humanity.
However, Eren says that he’s not disappointed, rather he’s simply surprised by Levi’s strict rule-following. Here Eren is, under the care of Humanity’s Strongest, one of his idols, and he’s not disappointed nor does he care about Levi’s personality or physical appearance. He hadn’t created a flawless image of Levi being the perfect hero, because Eren doesn’t care what Levi looks like or how he speaks. What Eren admires about Levi is what he does and has done, because to him that’s what really matters.