Disclaimer: I in no way, shape, or form own Danny Phantom and it belongs to it respective owners and I am in no way attempting to make a profit from this work of fiction.
Anyway, now that the dreaded disclaimer is out of the way, on with the story!
This is just a random theory I came up with concerning Danny Phantom and I've watched the entire series so I think it has some evidence in the show.
Danny, by gaining his powers from activating the Ghost Portal, has a type of bond to the Ghost Zone, and this next part is pure theory but I can back it up, and acts as an anchor to it and the real world.
This is a little far-fetched but I'm pretty sure of it and once again this is a theory but I have evidence to back it up.
So let's look at Clockwork, the ghost responsible for time and the continuing order and existence of the world.
Why would he even risk Danny possibly turning evil and wiping out the world when he could just wipe him from the timeline? Because Danny binds the Human World to the Ghost Zone and without it he could possibly lose his influence on the Human World timestream and with it the majority of his power since it has to come from somewhere and losing an entire source of power could cause a lot of damage to his position in the Ghost Zone, that is if he draws it off of the timestreams of the worlds he can move through but that's a theory for another day.
But back to the point of this, Clockwork, clearly a very powerful being with his mastery of space and time, didn't need Danny to defeat Dan in "The Ultimate Enemy" he could have easily just have deleted Danny or him gaining his ghost powers from the timestream but he didn't.
Why, because he can't as that would leave him with half of his power gone.
This also brings to light why the ghosts really helped Danny during "Phantom Planet" because Vlad could clearly survive in space so it would make sense that the ghosts would simply flee the Ghost Zone and head into space since they don't need either food or water to survive but maybe they do need something to survive.
Vlad being a hybrid of Ghost and Human could survive without the one thing every Ghost needs, the ectoplasm rich world of the Ghost Zone and this is seen in the episode "D-Stabilized" when Dani, slowly falling apart throughout the entire episode, is brought to full health and better by Danny's use of the Ecto-Dejector, a device which, another theory here, used a modified version of ectoplasm in it in an attempt to destroy ghosts but knowing the Fenton family it does the opposite and strengthens them. So with Dani being a clone, composed primarily of ectoplasm from the earlier episode involving her titled "Kindred Spirits" where overexertion of herself was turning her into what was most likely ectoplasm as that was the basis for her body, with Vlad not having much to work with in other materials.
But back to the topic at hand, the ghost didn't help Danny save the world because their world would end with the Human World, which is highly unlikely too since Clockwork allowed Dan to terrorize the world, Pariah Dark to plan an entire invasion, and Undergrowth to cover it in plants, but because they would all lose their access to the Earth, and the dimension it resided in, if the planet went because the kid would do anything to attempt to save the world, even if it meant his death.
They didn't want to lose their own personal playground of the Human World so they helped him, not out of the goodness of their nonexistent hearts but because they needed to so they could keep their access to the Human World.
And when you think about it, this explained Danny and later Dan's powers.
So let's look at a few of Dan's powers and what they equal to.
Ghostly Wail equals Ember McLain.
Ability to open portals into the Ghost Zone equals Wulf.
Flaming hair and most likely Pyrokinesis equals Vortex, or maybe Pariah Dark.
So yeah, Danny has a lot of potential since he is connected to a limitless pool of energy by his connection to the Ghost Zone as an anchor to the Human World.
Now you may be saying that Vlad is an anchor too but he isn't.
The Fenton Ghost Portal was much larger and more powerful than the ones that gave Vlad his Ghost Powers and just looking at the growth rate of both shows that Danny is much more powerful than Vlad.
During their first encounter Vlad completely destroyed the still new to his powers Danny but at their last encounter Danny was able to match if not exceed Vlad and let's not forget the raw power Danny taps into when he's angered or annoyed, able to completely obliterate a miniature golf course with a single attack in "Kindred Spirits".
So to wrap all of this up, Danny has the potential to become godlike is he continues training because he has a limitless pool of energy to draw from since he's an anchor to the Human World for the Ghost Zone by being charged with its energy when he activated it the first time.
Damn you Plot Bunnies, damn you!
They keep making me write oneshots anyway read and review on what you think of my theory and this may turn multi chapter so give me your theories and I'll see what I can do with them.
Peace.