Its more of a matter of Natsu not getting character development as to Happy getting some character development. There's almost no change in Natsu from the first episode till the episode that I watched. He's still the happy-go lucky kid that he always has been. His character development is pretty much non-existent. His personality itself is easy to grab-- the normal traits of a shonen series, you know: Eats a lot of food, thick-headed towards romance, hot temper and mostly fights without thinking, etc.
And once you do grab it, you'll easily predict his lines and actions in the later episodes. Since he does not go under any change at all, I was able to predict him with a good deal of accuracy. Its not bad to be predictable, but Fairy Tail takes that to new limits. It becomes boring to watch Natsu as soon as you recognize his personality. The one time he loses greatly is against Gildarts, but in the later episodes, there is absolutely no reference of that. He just forgets his lack of power back then, forgets how he lost and goes on with the same character personality.
Instead of seeing characters train, we just see them getting new power-ups which can hardly count as character development. In my opinion, characters make Fairy Tail, and character development ruins the same.
