One of my all time favorite movies has always been the Bad Seed. The Bad Seed was made in 1956. (before I was born!!!) This movie is so good even today. You should check out this little girl in action if you haven't already.
There have been other movies that have copied off of the concept of this movie like The Good Son. However, they have not come close until now. Orphan is excellent, if you like this genre of movies. I do!
Orphan even has a little extra than the original Bad Seed. Go see this movie. I recommend you see the Bad Seed 1st though so you can get an idea of the type of movie that Orphan is. Ooooooh it was good! I'm buying this movie when it comes on DVD.