So I know Butch's facts video got everyone in a tizzy about what ghosts are and are not in the Danny Phantom universe. And while I don't want to aggravate that any further, I think I managed to come up with a theory that seems to fall in pretty well with what Butch said.
For now, I'm just copying this from a comment I made on Derpyrebound's own theory blog post, which is an awesome theory in its own right that you should all check out. I'll fully explain my own in more detail later, but for now, here's the original comment:
...It also got me thinking about other theories to explain Butch's "monsters from another dimension" statement, and I think I have one of my own:
So, to give some background here, I've been playing the computer game, The Sims, for about 16 years now. And as the game has evolved, so has its own lore of supernatural creatures. Ghosts, zombies, vampires, werewolves, fairies - you name it, The Sims has it.
Now in the game, all these creatures are usually referred to as the "supernatural" or the "occult," and that got me thinking - what if we treat Butch's "monster" statement the same way? Instead of it being "monsters" versus "ghosts," they all become umbrella terms - "monsters" and "ghosts" are basically the same as saying "supernatural" or "occult" when used in a broad sense. (It basically becomes a case of "Ghosts" versus "ghosts" in a way. :P)
Poindexter, Ember, Cujo, the Dairy King, all those characters that used to be humans/animals and died, we can still consider them to be "ghosts" in the usual way that we define the word - these characters faced death and are now living their afterlives.
Wulf can be seen as a werewolf, and Frostbite and his people fall under the Yeti category. Cases can probably be made for zombies somewhere in the Ghost Zone. And even Vlad was supposed to be a vampire, and had it not been for censorship, we would've gotten that. And for all the characters that for now are "un-sortable," even they can be seen as basic "monsters" under the "supernatural" term (like that kid in "Prisoners of Love" - he'd be a monster).
What ties all these characters together and makes the show unique, no matter what "breed" of the supernatural/occult they are, is their powers and ectoplasm. That's what gives the show its twist.