A recent movie called Split is about a group of girls who is kidnapped by a man with MPD who cycles through twenty-two alternate personalities and at the end his twenty-third personality shows itself and it is pretty freaky according to the trailer. Although the man in the film seems to have been a sufferer of MPD for a long time so he would most likely have triple the amount of alter personalities that he has. Also most MPD patients are docile, although some can be dangerous, but there are not many.
A more realistic take on MPD is a book called Three written by Ted Decker, where the man character is terrorized by a mad man who gives a certain amount of time that has to do with three (three minutes, 9 minutes, 3 hours, 6 hours, etc.). He has to try and stop him, with help of his best friend Sam. At the end, he realizes that the mad man and Sam are only alternate personalities of himself. The reason for his personalities is because he was abused as a child, which follows in line with most MPD