Since the world we live has overwhelming amount of information, human brains must make lots of simplifications and crude assumptions in order to make the world understandable. Which means we do a lot misinterpretations, especially if the phenomenon we are observing is not familiar. And no one of us has an unchanged memory, the more we think about our experiences the less truthful they become. You don't have to be at all funny in your head to see things that don't really exist or remember something that hasn't happened.

Some sightings are no doubt rare or even unknown natural phenomena, but Occam's Razor is not kind to the extraterrestrial hypothesis.

Have you ever wondered, why amateur astronomers don't see UFOs even though they observe much more the sky than a casual person? It's not because they're afraid they're going to be ridiculed. Of course, you can always make the counterclaim that they misinterpret genuine alien spacecraft as natural phenomena.

UFOs as extraterrestrials are the modern equivalent of elves and angels. People believe to them because they seem so plausible. Humanoids are an interesting scientific phenomenon, but only from psychological and sociological sense.

And this post is off-topic.

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman