In Journey to the West by Wu Cheng 'En, what is the summary of the last chapter (Chapter 100), and what is the chapter's surprise ending?

In Chapter 100, the people of Chen Village are devastated when they discover that the four travelers have left. They use the food they have prepared for the travelers as sacrificial offerings, and from then on, yearly sacrifices are made in the Buddhas' honor.
The travelers eventually come to the Watching For the Scriptures Tower and are met by Emperor Taizong. Delighted to see them, the Emperor bids the Tang priest and his three companions follow him back to the palace. At the palace, the Emperor invites the Tang priest to sit in the throne hall; Monkey, Pig, and Friar Sand unpack the scrolls, and the Emperor demands to know how many scriptures there are and how the scriptures were found.
Sanzang (the Tang priest) answers that the Lord Buddha had originally given the travelers "blank, wordless versions" of the scriptures. In order to recover the real ones, the travelers had to hand over their "begging bowl of purple gold" to the two arhats, Ananda and Kasyapa. In all, there are thirty-five scriptures. The Emperor is pleased with Sanzang's words and orders the Protocol Office to hold a thanksgiving banquet in the Eastern Hall.
After the banquet, the four travelers return to the Hongfu Monastery, where they are welcomed by the monks. The next morning, the travelers are formally thanked by the Emperor for managing to retrieve all 5,048 rolls of the 35 scriptures; additionally, the formal words of acknowledgement and thanks for the travelers' accomplishment will be recorded as a "Preface to the Holy Teaching." The Emperor states that the scriptures will be translated for the edification of the Chinese people.
On the advice of Sanzang, the Emperor tasks "the officials of the Hanlin Academy and the Palace Secretariat to copy out the true scriptures" and the Copying Monastery to publish copies for the people. The original scriptures will be stored as "great treasures." Next, the Emperor asks Sanzang to expound upon the scriptures at the Monastery of the Wild Goose Stupa. However, before Sanzang can begin, the Eight Vajrapanis appear to take the four travelers back West.
Back West at the Vulture Peak, the Tathagata gives the four travelers their rewards for having completed their mission successfully. They are each promoted to bureaucratic posts in Heaven. Sanzang is made the Candana-punya Buddha, Sun Wukong is made the Victorious Fighting Buddha, Zhu Wuneng is made the Altar Cleanser, and Sha Wujing is made the Golden Arhat. Meanwhile, the travelers' faithful horse is made a Heavenly Dragon of the Eight Classes of Being. Also, Monkey is allowed to be rid of Guanyin's magic golden band. Now that he is a Buddha, he need no longer wear it on his head.
The chapter ends with all of Heaven paying homage to the Buddhas. If you're looking for the surprise ending, I suspect it is the moment when the four travelers are abruptly taken back to the West by the Eight Vajrapanis and rewarded for their faithful work.