When referring to the plural of a movie title (in the case where the movie has sequels), do you have to obey the pluralization rules of the last word in the title, or do you just add -s or -es to the end? For example, if I wanted to watch each of The Matrix movies, would I say, "Let's watch The Matrixes" or "Let's watch The Matrices?" The latter sounds kind of silly, but is it proper?
I think it's best to avoid changing the movie title at all; it should be left intact as the author intended it to be. In your example, I'd paraphrase, and say:
Let's watch The Matrix movies!
Let's watch The Matrix trilogy!