1. Daario Naharis - Game of Thrones
Game of Thrones doesn't exactly have a great track record for maintaining casting continuity in anything other than their main group of lead actors. They are switched in and out casually, and just as we can never be sure if out favorite characters are going to survive their run on the show, we're equally uncertain if they will even be played by the same actors. We've seen a new Tommen Baratheon, but it's more or less understandable that they made the switch from Callum Wharry to Dean-Charles Chapman. After all, the character went for a long spell where he wasn't featured heavily on the show, and no one would have really noticed that they changed actors. In addition, they made the creative decision to age up the character by a few years, and Dean-Charles Chapman has the acting experience to handle the more developed role. But a more egregious example is the recast of Daario Naharis, a crucial member of Daenarys's squad. Between seasons 3 and 4, actor Ed Skrein somehow morphed into Michael Huisman, who is equally attractive but very different looking. Apparently Skrein left Game of Thrones to work on a new Transporter film, which is obviously a better career move than a featured role on the most popular shows on television.