These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Ancient Aliens
Ensemble Darkhorse: Giorgio A. Tsoukalos. The new season even features him accompanying the History Channel's team. It's gotta be the hair.
Narm: Pretty much the whole reason to watch the show. A particularly memorable promo had this line from Tsoukalos:
Tsoulalos: The Large Hadron Collider bears an uncanny resemblance to the Mayan Calender. Coincidence? I think not.
Seasonal Rot: Not that the show is generally considered high quality to begin with, but the later seasons have essentially just repeated things already done in previous episodes or have to reach further and further to connect aliens with absolutely anything. To the point that one episode was a thin excuse to discuss superheroes because they were based on archetypes that might have been inspired by aliens.
So Bad, It's Good: What else could a show that makes Sunn Classic Pictures documentaries look sober and reasonable be?
Unfortunate Implications: When one strips away the various pieces of flat-out wrong information produced on the show, it can fall into this: a great deal of the "alien" artifacts or human sites built "with alien assistance" are from pre-Columbian civilizations or sub-Saharan Africa, the implication being that these civilizations were too backward or stupid to create such impressive structures. For instance, the show once claimed that Puma Punku, a fifth century Aymara site in the Bolivian Andes, was "the only site created directly by extra-terrestrials". At the same time as Puma Punku was constructed, the Romans were building equally-if-not-more advanced stone structures...but of course those stupid Amerindians couldn't build anything white people could, they must have been helped by aliens!note On the other hand, the show erroneously claimed Puma Punku was a couple of thousand years older than it is, so there's that. It's not hugely far-removed from the 19th century theories that Great Zimbabwe was built by "southern Jews".