ANSWER
Charlie Kaufman and his twin brother Donald were nominated for their screenplay adaptation for the movie "Adaptation", which is a movie is about a writer (Charlie Kaufman, played by Nicholas Cage) and his twin brother (Donald, also played by Nicholas Cage) who struggle to create a screenplay adaptation for a movie.
Now for the unusual part - Donald Kaufman doesn't actually exist, despite being listed in the movie's credits.
Over the years a number of people have been nominated under pseudonyms, but this is the first time the Academy has ever nominated a completely fictional person. However, Academy officials have said that if the brothers win, they must share a single statue.
WHO GOT IT RIGHT: Marc Quinlivan, Yanitz Grinell, Trish Boggs, JP Weigt, Marika Thiessen, Allan Christensen, Robert Walker, Bob Milligan, Kristy Morgan, and Jim Ahumada.