There are two different versions of the "Mary Shaw" poem. In the movie the poem goes, "Beware the stare of Mary Shaw. She had no children only dolls. And if you see her in your dreams, do not ever, ever scream." On the trailer it was, "Beware the stare of Mary Shaw. She had no children, only dolls. And if you see her do not scream, she'll rip your tongue out at the seam."
When Detective Lipton confronts Jamie in the hotel room after Jamie tries to bury the doll, there are several occasions when Lipton's mouth does not match the words being spoken between cuts or isn't moving at all.
(at around 1h 0 mins) When Jamie leaves his father's house to meet Henry at the theatre, a member of the production crew can clearly be seen standing behind a bush in the garden as his car reverses.
It turns out the main character's step-mother is the 'perfect puppet' with Mary Shaw's spirit living inside.
Q
List: Ventriloquists who have disturbing relationships with their dummies
A
See: this FAQ entry
Q
What are the differences between the theatrical version and the Unrated Version?
A
It is noticeable that in the unrated version it was tried to raise the tension via computer again. Additionally to the usual deepening of the story, some disgusting tongue-effects have been added. While the evil witch does not have such a flexible and slobbery thing in the R-rated version, several scenes of the unrated version have been spiced up, others are completely additional.
A detailed comparison between both versions can be found here.