I love Ancient Aliens. But I only accept some of what they are saying as plausible, and I think they do their theory a disservice by trying to connect every single thing that happened throughout history. It is very possible Aliens are real and did visit the Earth, but to suggest humans couldn't have stacked stones on top of one another to build monuments or develop writing or whatever without alien assistance is not giving humanity enough credit. They aren't suggesting aliens helped us built cellphones or computers today, so why did aliens have to give us writing thousands of years ago?
There's also that David Childress guy on there who I am unable to take seriously after this one episode where he said NASA crashed a probe into the moon and the whole moon rang like a bell for hours afterwards. WTF? I looked on google and never could find any such thing, so that dude must be smoking something or he's just nuts. Its fun to watch him and the nutty things he says about magical energy fields and whatever, but I would think the more reasonable ancient alien theorists would want to distance themselves from him, because he makes all of them look bad by association.