Regarding the person of the twelfth Imam, more needs to be said. Both Shiites and Sunnis accept the Koranic teachings on the Apocalypse, at which time they too look for the second coming of Christ. However, in Islamic doctrine the way for Christ’s return will be prepared by the Mahdi, in a fashion somewhat like that of John the Baptist the first time around.
The difference between Sunni and Shiite eschatology lies in the Shiite belief that the Mahdi is in fact the person who was the twelfth Imam, and that Muhammad al-Mahdi did not die but was granted supernatural long life and has only receded from view by a process of occultation (ghaybah), which can be compared to the taking up of Elijah via the chariot of fire. For Shiites, it is precisely this person who will reappear, publicly, when the end arrives.
Sunnis, for their part, do not claim to know who the Mahdi will be, but rather they simply expect a figure to appear with that name at the appointed time.
We will pause here to note that eschatological thought does not factor into Islamic culture in the same way that the “rapture” and the second coming of Christ factors into Christian popular culture, particularly in the United States where books, movies, and sermons abound with prophecies and imaginative depictions of who will be saved and who will be damned, and what this will look like.