Aliens are living things, that aren't of the same race, or area. So, yes, aliens do exist.

To answer the OP, it is highly unlikely that aliens assisted in the building of the pyramids. If they shaped the world then, they'd shape the world now. With modern communication, we'd know if extraterrestrials were doing anything notable.

To answer seriously, I think there are aliens, but not in such a way we would all like to think of. I believe there must be some kinds of micro organisms somewhere.

No, I believe in ghosts.

Well, actually Aliens don't exist, but other life forms do.
There are tons of planets in this whole universe.
Just think about it, we are in one planet.........are there any living creatures on any other planets?

It might be possible that there are life on other planets. But the chances are probably so slim. I dont believe though.

I'm religious, so no it's impossible.
Loljks.
I believe there are many aliens, but they probably have the same intelligence as the animals we have here. Maybe 1 or 2 races that are as smart as us or smarter, but that's it.
Heck, they might even be looking for us right now or probably extinct due to not enough resources or something.
(i typed this on my phone on the way to school, so i might not make sense.)
Also, all ufo 'siteings' are fake. I mean seriously some guy in the 1900s most likely made a popular show about aliens, which had aliens drive sauce-like vehicles and were green and from there people believed this was what aliens looked like.. What are the chances of real life aliens having the exact same type of ship?

Yes i believe in aliens, but i am not sure about weather or not we've made "contact"

But , i'm still doesn't believe in alien !
Could someone prove it ?

aliens are real they came to earth i believe in them