in the 2004 movie, why does Erik have a mini model of the stage and little búp bê and stuff?? cause if bạn ask me that's just kinda creepy...(especially when he starts switching their heads around)

Well, he can only write âm nhạc and obsess over Christine for so long, right? What else is a Phantom that's hanging about the opera to do, besides use up some of his endless time creating a mini stage and singers? The switching heads is mainly an slightly-overly theatrical way of symbolizing that he wants Christine instead of Carlotta to sing the Countess.
And yes, it is a little creepy... hey, he's a creepy guy. It works.