Sure they do ! They've been here before. They may come back again someday!
Do aliens exist?
Yes
Yes, we do.
I think it's ridiculous to suggest that they don't when the statistcs and amount of space that we don't know about means that it is overwhelmingly likely they do exist.
I think they do ^^
Yes. In fact, we humans are actually the aliens to this here planet. Over ten thousand years ago, a group of aliens, known as the Ancients, came here from an unknown galaxy and made earth their home. After a massive plague almost wiped them out, they decided to leave earth in their city-ship, Atlantis. We are the second evolution of the Ancients.
According to the dictionary, they do.