1) A number of scholars believe that there are extraterrestrial beings. One hadith from Imam Ali (a) indicates there are “nations” in the stars just as there are nations on earth. Some believe this is a reference to extraterrestrial beings.
2) As for the pyramids, we don’t know how they were built or who exactly built them. Some have suggested that the Jinns who worked for Prophet Solomon built them. Some have suggested that the builders of the pyramids got their knowledge for the prophets of their time. We don’t have any evidence for these theories, but they are out there.