Ed Skrein As Daario Naharis In "Game Of Thrones", Replaced By Michiel Huisman
Game of Thrones is not a stranger to recasting minor characters. One of the most visible ones is Daario Naharis. Ed Skrein was the original actor to portray the mercenary, but because of political reasons and (more likely) the wish to act in a Transporter movie, he had to leave the series. Michiel Huisman replaced the actor for the rest of the seasons.
Also, how would anyone be able to tell when some background character in GoT was replaced? There were a ton of them, and they all looked the same.