Perhaps you see, a small little green humaniod with big buggy eyes and a triangular face? Or maybe you see a large hunking repilitain like humaniod with a jaw of rows of pointy teeth and snake-like eyes. Or, you picture, Nordics. But let's go through all of these quickly, starting with:
Now, appearance-wise Nordics aren't well.. All that abnormal. You see, Nordic aliens, or Pleiadians, are rather tall (Around 6 to 7 feet or 1.8 m to 2.1 m tall) and looking rather well... Nordic, with long blond hair, blue eyes and fair skin. So, imagine a very tall Germanic person or a Nord from Skyrim but if they where taller.
Apparently, a guy by the name of George Adamski reported these Nordic aliens in the 1950s. They were apparently, very chill folks who were benovolent, communicated through telepathy and were gracful and beautiful.
Examples of their behaviour seems to indicated that these guys are really trying to help humans advance into the future and to enlightenment. You might have heard about Nordic's because of New Age religions, but I am not savy to the religious meaning of these guys so look for that yourself.
I do, however, know about a film called The Day the Earth Stood Still, a 1951 film I actually watched. Uh, I'm not certain whether the main alien guy was actually a Plediadian/Nordic or was just heavily inspired by one. But these guys are very interesting and I kinda wished they was as popular as reptilians or LGM.
Most of these Nordics are mostly just curious and honestly, it just reminds me of less scary Fae. Like, Fae are also so above humanity that they don't understand how humans work, but it's less like a pompous bastard, if that makes sense? It's like humans looking down at animals, trying to figure them out, understand but not doing it perfectly well.
Everyone knows reptilian aliens, or at least everyone does. The main conspiracy theory idea of it was apparently originated because of Conan the Barbarian popularising the idea of humaiod lizards which spread over to the conspiracy theory world, but either way the idea of lizard aliens are pretty neat.
Unlike Nordics, most Replitians are described as been horribly carnivorious and humans apparenly being the tastiest options for them here. But they don't just want to eat us now, if that makes sense? instead apparently trying to play human politics to get snacks.
Honestly, Reptilians aren't as interesting as the Nordics to me. Mostly because they're so common in pop-culture I firmly believe that all I need to say is "reptilian aliens" and bam, you can not only imagine the idea of what it looks like but it also how they function and what they want with humanity. Meanwhile, Nordics are benovolent, which I feel is something thats more alien to us humans.
Well, due to Reptilians conspiracy theories, it's kinda hard to talk about them and not mention the sheer amount of conspiracies built up here. Most everyone has someone they don't like, hell even I do, but odds are they're not a reptilian. Reptilians are somewhat respectable as all they want to do with humans is eat us, it's the humans who can make full-fledged horror. So, You don't gotta dehumanise them, just let them be evil humans, you know?
Everyone knows and loves Greys. You know them, right dear reader? Those cute little humaniods with the big heads and buggy black eyes. They're apparently called Zeta Reticulans, but I'm sure almost everyone just calls them Greys.
Some theories suggest that Greys are the geneticially-engineered work-force of repilians. Mostly so that the Grey's do the busy work for the Reptilians which is a sad reason for existance, I must say. Just imagine being created to solely be worker.
Another theory, is that Greys are humans from years into the future where we became space-faring entities. In that case their more akin to benovolent little guys curious about old school humans.
Also, apparently they're unable or unwilling to talk to us instead using telepathy to communicate because for some reason speech is beneath almost all aliens.
Honestly, most Greys have more information on them than other aliens. Mostly because we've had more to talk about with these little guys. They are the most common encounters of the third kind. Think back to the first alien story you've heard, and odds were it might've been a Grey in it.
Personally, Grey's are just classic aliens. They're damn near iconic with that unique look and mutiple tales going on about it.
Not extraterrestials per say, but the Men In Black are really common in Conspiracy Theories in general. In honesty, the Men In Black are used as any stand in for any government cover-up of any conspiracy theory.
It kinda started in 1947 and well, everyones now running with it from here on out. I don't really fear the Men In Black, mostly because even if I did unvail something that I shouldn't, wouldn't it be easier to cover it up by just mudding the waters, poisoning the well or any manner of bribery instead of assassination?
What I'm trying to say, is that if you are a MIB agent and want me quiet, please just try to pay me first. I may love conspiracy theories, but I really love money more.