I have seen fiction outright stating, "This is a true story" - i.e. Fargo, or the rather-less-good "The Sleep Experiment". The former at least has great production values and is actually taking inspiration from real events. The latter is 110% made up.

In the case of Fargo the cohen brothers chose to make a movie in the “real crime story” genre, and that title card sets the tone. Any overlap with actual crimes is almost beside the point. (As a viewer this really bugs me — there is such a thing as truth!)

The show also heavily plays with fable.

UFO sightings were a real common thing in Minnesota, so in the show a real UFO comes, because it’s people telling the story as they saw it. The true part is that people truly tell the stories, and in that sense, since they told this story it truly is a true story.

Did you watch the whole first season since I made my comment? Or why did you think somebody was going to be an alien in S01?

I saw a screenshot that showed a UFO in a review of the show and I figured it must have aliens in it.

The original movie had Steve Buscemi. He kind of looks like an alien. Does that count?

There aren’t UFOs in season 1 though.

Did you somehow watch season 2 without watching season 1?

I’m also not sure if none of the characters being aliens really makes the show stupid. That analysis would apply to quite a few shows.

There's like a gradient of "truthiness" in movies that ranges from "This is a true story" to "inspired by real events" (which is the least reliable of all).

Well based on a true story has no real percentage of trueness. Cocaine Bear is based on a true story. It might be more correct to say inspired by a true story but it is based on a true story.

Based on a true story just means someone somewhere said something like this happened. Bloodsport is a great example of a movie that is based on a true story but that true story turned out to be entirely false.

Paul Harvey’s “The Rest of the Story”. Stories that were often too good to be true, because many of them weren’t.