They haven't significantly changed Elijah's character I don't think, but for me it was all "whoa" and really exciting everytime Elijah got undaggered lol, and then when they did start using him more in season 4 I found myself getting more and more turned off by his character. Things like his hypocritical treatment of Katherine really stood out to me when he started lording it over Katherine and how he doesn't know if he can ever trust her, completely ignoring that Klaus and Elijah were the reason she had to flee for her life in the first place. That stuff was no doubt always there and consistent with his prior characterisation, but when he became more of a full-time character that's when it started standing out to me that he judged Elena and Katherine by very different standards and had a total madonna/whore complex.

Both Castiel and Elijah did, but their performance was singular and what made them so popular wasn't replicated with subsequent characters

I think a lot of people were underwhelmed by the presentation of Klaus after all the build-up because Elijah had led us to expect an even more awesome Original, and instead Klaus never felt like a really old vampire in the same way. Meh he always comes across more as someone who was changed in the 19th or 20th century to me


Actually, right up until the end, I thought they were going to succeed at putting him in the coffin.

I really thought that too :( It would have been a nice send-off too with the intense looks between Stefan and Klaus, so it's a real shame that they kept him round for so long after that when there wasnt all that much point to him still being in Mystic Falls for season 4. I think his crush on Caroline was meant to be one of the ways of giving him more dimension after they choose not to kill him off (and I know the actor was campaigning on twitter for a love interest for those reasons), but that was when his character first became ridiculous to me when he just instantly seemed to fall for her and drew pictures of her with his horse :P