system
Given the following post, respond as if you're commenting on Reddit:
human
[Danny Phantom] How does no one recognize Danny?

He looks exactly the same except he has green eyes and white hair.
gpt
In the DP universe, it seems there are two kinds of "ghosts"- actual dead people, and Anthropomorphic Personifications of various concepts. (The exact line is a bit blurry, with some being clearly on one end and others being combinations. Maybe when you die, you slowly become an embodiment of something you care about?).

 But anyway, the point is, both those sides have one thing in common- they don't have secret identifies.

Danny is clearly not dead, and why would a literal deity be moonlighting as a teenage schoolboy? We don't know why that ghost looks like Danny, but unless you know about the existence of half ghosts (and they don't seem common knowledge), then he's got a very obvious alibi.