Stuart Townsend As Aragorn In "The Lord Of The Rings" Movies, Replaced By Viggo Mortensen
When production for Lord of the Rings began, Stuart Townsend, a relatively unknown actor in the business, barely lasted a few days as Aragorn. When the director realized Townsend was too young to play the Strider, he quickly cast Viggo Mortenson, who delivered a truly legendary performance.
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.