"Have I ever told you about the guy who used to live on my block? He is actually a pointy-eared, green-blooded alien, from a civilization which endeavors to function by emotionless logic."
"Um, you mean like a Vulcan, from Star Trek?"
"No, nothing at all like Star Trek, because this alien former neighbor of mine belongs to an ancient order of warriors for peace and justice who wield swords made of laser light, and have power over a mystical unifying force which suffuses the Universe."
"So.... like the Jedi in Star Wars."
"Have you not been listening? My former neighbor is obviously a real person, and not some made up 'story' derived from Star Wars, because Star Wars has no pointy-eared, green-blooded, emotionlessly logical alien. And he is obviously not some story derived from Star Trek, because Star Trek has no swords made of laser light and no mystical unifying force suffusing its Universe. Besides, there's more -- you see, my former neighbor was sent here in a spaceship as an infant, because his own planet was unstable and was going to explode."
"Okay, now this sounds like a mix of Star Trek and Star Wars and Superman."
"Don't be ridiculous -- Superman shoots freakin' laser beams out of his eyes and is vulnerable to Kryptonite, from his native planet. But my former neighbor doesn't shoot laser beams or anything else from his eyes, and isn't at all affected by Kryptonite. Plus I already told you, he has green blood. Superman doesn't have green blood. Or pointy ears. So, obviously he can't be some story derived from Superman -- I'm telling you, he's a real pointy-eared laser-sword-wielding logical alien, sent as a baby from an exploded planet to Earth, where he gains strength from our yellow sun!!"
"And you didn't get any of this from, I don't know, maybe reading some comic books? Watching TV?"
"No, I got none of this from any of that. I heard all this directly, straight from the kids of the people who lived on the house on the other side of the street, who heard it from their parents, who heard it directly from my former neighbor."
"Wait -- so, your former neighbor didn't tell you this himself? He told some other people this?"
"Tell me? No, I've never even met the guy. He moved out before I even lived there. But my other neighbors across the street, their parents knew these things about him, and their kids even wrote all this down. Years ago."
"And how do you know the parents who told the kids all this didn't, maybe, mix in a little sci-fi. Even by accident, mixing things in? Or that the kids didn't mix some of these sci-fi things in?"
"Because that makes no sense -- why would they mix anything in? Look, you're overthinking this, my former neighbor obviously isn't a fictional character because there is no fictional character which combines all of these characteristics which he's been, I stress, recorded in writing as having. I mean, look, if I tell you my former neighbor breathed oxygen and ate food, would you conclude he was a fictional mix-up because everybody else breathes oxygen and eats food?"
"But we see people every day doing those things. We don't see pointy-eared green-blooded logic-observing aliens at all, except in Star Trek and things derived from it. We don't see laser-sword-wielding force users at all, except in Star Wars or its copycats. And we don't see an alien from a doomed planet sent to Earth in a spaceship except in Superman, and knock-offs of it."
"I'm sorry, but I hardly see that as proof that what I've heard about my former neighbor is untrue. In fact, maybe you've just misremembered all your sci-fi stories."
"Well I guess we'll have to agree to disagree."
"I guess. So, hey, have I ever told you about the religion I follow?"