MORE Ghost Ideas.
Apparently people loved the Truck-Kun being a Ghost idea, so that got me thinking. Technically how much could we stretch the limits of what becomes a "Ghost" in the Realms?
From different media and headcanons I've seen, there are usually one of 3 things that needs to happen to become a ghost.
One is high enough ectoplasm, or to be ectocontaminated enough to pretty much be guaranteed a spot in the Zone. Two, is high emotions. Ember is a great example, because she would have been SO angry at being forgotten that she formed a Ghost.
Lastly is Obsession or regret. You'd have to be Obsessed with something back when you were alive, or that you'd regret you didn't get to do something while alive - and that is the only thing you can think of, and that gives you a chance to become a Ghost.
So if you think about it, you can stretch different media on how they become a Ghost.
Let's say, a certain Spirit wanted to Protect someone. Wanted to Save them so much, that after everything - when they move on, they become a Ghost of the Realms. Charolette Emily is a perfect candidate! Obsessing over Saving and Protecting Children.
Cassidy too! Both options are from FNAF if you JUST SQUINT at it hard enough. What about UNDERTALE? Flowey is Asriel without a Soul, and Fandom dictates Chara didn't wake up or follow Frisk around until ... well, Frisk showed up. So where were their Souls while waiting? GHOST ZONE!
Hell, you can pull some of the most insane crap here too. What about the PRIME SOULS from ULTRAKILL? Minos dies, with regrets of not having been able to avenge his people - BOOM, Ghost. Sisyphus probably doesn't count, again, SQUINT at it. Obsessing over rebelling and having an unshakable will? GHOST.
If JASON TODD became a Ghost of the Realms for a hot minute, before being brought back to life, you can push this as far as possible. And enter the Realms of ABSURDITY.
Truck-Kun became a Ghost, who's to say others haven't?!
How about MLP? It's NEVER explained where the Sirens came from, and they feed on Negative Emotions. Maybe they were from the Realms or something, and came to Equestria? Again, not exactly plausible - but if you SQUINT.
Pony of Shadows? Well of Shade in the Hollow Shades, but where does the entity come from anyway? GHOOOOOST ZOOOONE!
So many possibilities here for insane absurdities, all you have to do.
Is SQUINT.

















