From the LOTR trilogy I know that cast from visual audio and technical departments wish to play cameo in the movies. I remember Peter Jackson appeared in the Fellowship of the Ring in the Dancing Pony Scene. In the Hobbit I saw him as a cameo again in the Dancing Pony scene.
I wished to see Aragorn in the Hobbit as well. But in the original book Aragorn did not appear so Viggo Mortensen did not want to participate in The Hobbit although this was discussed initially.
I also did not know Nicolas Cage was offered for the Aragorn part. I like Cage very very much but I am happy to see Viggo as Aragron in the end.