I dont personally thing pyramid was built by alien or creature from another planet. There are lots of things we still need to explore. We still may have egyptian tech/knowledge to unearth.
About the creation of the SOURCE ( God or the Alien), what I believe is we cannot think outside certain boundaries. We have limitation of everythin including imagination. Try to imagine outside the universe, try to find the source of the creation, try to find the reality after death etc.

I will check this post when I sober up ;)