The internet has been a double edged sword for the study of the paranormal. On the one hand, there's a lot of information that you can find online which ordinarily wouldn't be available. On the other hand, false information can spread like wildfire. This type of behavior is particularly encouraged by reddit and youtube. Redditors are infamous for not putting in the work in search of karma (even when they claim to "solve" something the real work was inevitably done off site, such as places like The Cutting Room Floor, the Lost Media Wiki, or good old image boards.) On youtube the eternal quest to appease "the algorithm" means serving up different mixtures of popular stories with slightly different publishing values. There are some channels that clearly put in the work, like Beyond Creepy, The Missing Engima or (if we expand the topic to general Fortean folklore) Pseudiom. But for each channel like that there are dozens more which talk about "Missing 411" cases despite obviously never having gone into the wilderness. (You see this both from people acting like a long hike is a death sentence and those who say things like "why didn't he simply walk to town for five miles directly through dense underbrush?")
One topic that has become popular in this sphere is the idea of Indrid Cold: The Smiling Man. This is something that I've always found weird because I knew who Indrid Cold was before seeing any video about him on youtube. Indrid Cold was (supposedly) an alien visitor who contacted one Woodrow "Woody" Derenberger on a cold night in 1966. This is most famously related in John Keel's The Mothman Prophecies, which I have read several times. Woodrow wrote a book about his experiences, titled Visitors from Lanulos, and his daughter Taunia recently wrote a book titled Beyond Lanulos: Our Fifty Years with Indrid Cold. I haven't read either of these. In Keel's book the scene is presented that Indrid Cold comes down in a spaceship, looking basically like a normal man, and contacts Derenberger, first telepathically (though I believe later they talked normally.) Cold asked Derenberger about the nearby settlement and said he would return. He did, apparently dozens of times over decades according to Taunia. In these meetings Indrid Cold revealed to Woodrow that he was from the planet Lanulos in the Ganymede sytem which was much like our own, except a paradise with no war, disease, etc. These sightings made Derenberger a celebrity. You can find various interviews of him at the time. Indrid Cold would give messages to the investigator John Keel through Derenberger as an intermediary, though I do not think that anyone outside of Derenberger's family ever had direct contact with the vistor (despite his promises.) Things get more complicated with Derenberger being visited by other investigators such as the official (NICAP) and the more mysterious (the prototypes of the "men in black.") Eventually other alien acquaintances of Cold's also visited the Derenberger family, and they also took Derenberger to Lanulos. (Derenberger thought that time travel must be involed since the trips did not take as long as they should have, even with faster than light travel.)
And... that's about it. Despite the massive amount of publicity that Woodrow Derenberger got at the time, and the prominence he plays in Keel's book, nothing really happens other than Derenberger talking with Cold's companions and visiting Lanulos. No one else gets involved, there are no reveals of aliens to the public, no one dies. The only creepy thing about this is the weird interest the aliens take in Derenberger and his family specifically, and some details of the "utopian" Lanulos (like the insistence that clothing is unnecessary there, or how mundane and non-high tech it seems.) I haven't read either Woodrow's book or that of his daughter, but my understanding is that they mainly talk about variations of this sort of visitation happening over the years.
Of course, if you search for Indrid Cold online now you're sure to hear him called "the Smiling Man" or "the Grinning Man." You'll see drawings of him that have a distorted smile like Gwynplaine in The Man Who Laughs. It is said that Indrid Cold had an eerily inhuman appearance, as if he was attempting to appear human, but couldn't quite get the details right. And his smile never goes away. The fact that he comes from the planet Lanulos, if it is mentioned at all, is almost an afterthought. The real attention is paid to his "cold" smile.
If you go to The Mothman Prophecies here is how Indrid Cold is described:
The stranger was about five feet ten inches tall with long, dark hair combed straight back. His skin was heavily tanned. Grinning broadly, his arms crossed and his hands tucked under his armpits, he walked to the panel truck. He was wearing a dark topcoat. Underneath it Woody could see some kind of garment made of glistening greenish material almost metallic in appearance.
The next paragraph refers to Cold as "the grinning man," which was probably done because Cold had not yet given Woody his name. That's it for stressing the smile. Nothing about this description sounds inhuman, and if there's anything bizarre about Cold's appearance it's his outfit, not his facial expression. Since these are the only two references to Cold's smile, it definitely is not suggested that he never stopped similing. No mention is made of Cold smiling when he is leaving, for example. (Though I guess you could argue that it isn't said that he wasn't smiling.) I haven't read the books from the Derenbergers', but I have heard statements from both of them in interviews. Their descriptions never gave me any impression that Cold and his companions looked inhuman in any way. They were essentially normal people who came happened to come from another planet and had some additional abilities (such as telepathy.)
To me the interesting question is then: how did the "grinning man" come about? It wasn't from Derenberger, and it wasn't from Keel. Perhaps it is simple exagerration, which further gets magnified by youtube and reddit culture. Keel mentions Cold grinning twice. Someone summarizes the encounter says "Cold grinned frequently in the encounter." Someone who sees only the summary further twists it to "Cold never stopped grinning in the encounter." This then becomes "Cold never stops grinning, ever, and his smile was creepy and impossible." A game of telephone basically. Something else in support of this is that many of the modern descriptions of Cold describe him as extremely tall, or even impossibly, inhumanly tall. But Keel clearly states taht Cold was five feet ten inches tall. That certainly isn't short, but not especially tall. I've seen sites that claim that this is average male height in Minnesota and Alaska. Average heights were lower in the 60's and so calling Cold "tall" is fair, but there's really nothing special about this height. However, it's easy to imagine the description going from "five foot ten inches" to "a tall man" to "a very tall man" and finally "inhumanly tall man", especially when paired with the other inhuman features which had entered into the description.
A bigger question might be, how did Cold get to be so actively creepy? Keel notes that one of the weirdest thing about the Cold encounters is precisely how mundane they are. Cold is not a threatening figure, nor really a messianic figure (despite his idyllic homeworld.) He's just a guy from another world. But now he is a horror icon. Now this part I do have some insight into. The movie adaptation surely has some blame. In the movie adpatation of The Mothman Prophecies the character of Indrid Cold is made supremely creepy in conversations like this one. Indrid Cold definitely didn't have a weird voice like that. While he had telepathy, he wasn't all knowing. The movie conflates him with the Mothman in the statement that what Cold looks like "depends on who's looking." Now in terms of the movie, I think this was necessary to make a more coherent story. Movies need to make some sense, real life doesn't. There is a similar thing done later. In the book Keel talks about a lot of Fortean events, not just those that happened in Point Pleasant. One is the phenomenon of people suddenly being addressed by a voice and being called a number. For example "Wake up number seven!" or "be prepared, number thirty eight!" These are usually isolated events, i.e. the communication doesn't continue and we aren't dealing with schizophrenics. In the book this is more or less a weird unconnected event. In the movie this is connected to the number of people who died in the Point Pleasant Silver Bridge collapse. That makes a more satisfying conclusion for a movie, but of course there was no connection in real life.
The trouble is that the number of people who saw the movie dwarf the number of people who read the book. The movie makers were clear that it was not a documentary or retelling of actual events. Instead it captures the "feel" of the paranormal. And the movie does do a good job of showing a constellation of weird events that seem connected in a hard to determine way (until the end), and which are constantly misdirecting the viewer (both in the movie and the audience watching the movie.) However, the average audience member would not realize this. Even if they were aware that some specific events changed, they would take the basic depiction of characters as accurate. Therefore the movie's depiction of Indrid Cold became the default. It's like how for decades Bela Lugosi completely defined what a vampire should be.
But this doesn't explain why Cold became a demented grinning man. We never see Cold in the movie, though the suggestion is that while he might be the same as the Mothman, presumably he would look normal if he wanted to (or if the looker was disposed to see a human.) He certainly isn't a tall, creepy man with a permanent smile. If we're going with movies, Indrid Cold's meme demeanor seems a lot more like the Mystery Man from Lost Highway. Maybe someone conflated the two characters, but I have no direct evidence for this. It's just a guess.
The real question is how Indrid Cold got conflated with this reddit post. (I'll understand if you do not go through the link, I feel dirty going to reddit to get it.) We have our modern depiction here, and it's definitely a creepypasta. (Despite what the author claims, this is obviously a BS story; no one describes a real event like this, not even a redditor.) Modern articles on Indrid Cold will link to this post as a modern sighting of him. However, you may note that the name "Indrid Cold" never actually appears in the story. Yet it will be always thrown in as part of the "lore." Why?
My guess is that some rando on reddit or youtube said that the creepypasta reminded him of how he thought Indrid Cold looked. Maybe he read the book and turned two references to grinning into a creepy smiling man. Maybe he brainstormed what kind of man could have that voice from the movie. Maybe he remembered the scene from Lost Highway and misremembered it as coming from The Mothman Prophecies. Who knows. In a way it doesn't even really matter, since the other people in the conversation certainly wouldn't fact check. What mattered is that the creepy tone was there. The idea of a sinister smiling man is an old one. I mean, I referenced "The Man Who Laughs" earlier, which is nearly a century old. There have been countless variations on the theme in movies, comic books, video games and cartoons since then. Pairing this powerful image with an actually documented paranormal incident (i.e. not just the normal reddit bs) made it much more interesting. Thus Indrid Cold became the grinning man.
Of course, I cannot prove that this is what happened. In order to do that I would have to sift through the comments on countless youtube and reddit posts, which sounds like hell even if search engines weren't useless and if both reddit and youtube didn't delete comments. It seems like the most plausible option though. The real sad part about this is that things are now too buried in unrelated natter that anyone new to the story will inevitably accept a lot of falsehoods. In that way, Indrid Cold serves as an object lesson about the general state of paranormal discussion online.