For instance, what doesn't make sense about a boy being attracted to a hot girl?

But it makes less sense that a boy would suddenly be attracted to a hot girl he never even thought about, previously. Unless she suddenly became hot (which is plausible, especially when it comes to teenage girls) or she said or did something, or something else happened that made him think of her in a completely new way and thus discovering she was hot. Both possibilities are plausible, but only the second one is interesting.