DPxDC Zero Gravity
Things Justice League knows about Danny Phantom:
He's dead (why, how, and for how long is unclear)
He's generally on the 'good' side (but contingency plans have been set up in case of 'future evil self' resurfacing, by Danny's own suggestion)
He's a figure of authority among other dead/neverborn/otherworldly/eldritch/magical beings (however, it's unclear to what kind of authority he holds and why)
He's dating one of the Bats (unclear to who, but none of them confirmed nor denied the fact, which is a confirmation on its own)
He absolutely hates only three things: toast, circus, and Christmas (neither of them explained)
His powerset is so wide that he can't even fully recount it (unclear if it's because he doesn't remember all his abilities or if he can't keep track of the new ones popping up spontaneously)
He's hot [whoever added this, you're not wrong, but I'm watching you - O.]
He has a grudge against Flash (unclear to why, but Flash seems to know the reason and won't budge regardless)
Of course, there are many more things to know about Danny Phantom, but they are mostly suspicions, rumors, and speculations. Like how sometimes the boy seems distracted and bored as if he is only going through a pre-written script; a sign of repeatedly going through the same day a few times too many, as the other time-travellers say. Or like how sometimes he knows too much - the boy is an expert in Kryptonian biology, to Clark's great surprise, and is more knowledgeable about Olympus politics than Diana herself.
There are also little things that are hard to notice and even harder to ignore once you do. How he never talks about family but likes listening to others talk about it. How he pointedly stays away from the medbay and any kind of medical staff. How he stops every time he passes one of the giant windows on the main floor of the Watchtower, smiling dreamily at the sight of vast, open space beyond it.
And then, there's The Thing that no one addresses.
When Danny Phantom doesn't pay attention, he unknowingly nullifies gravity.
The first time it happened, Bruce thought the Watchtower's artificial gravity collapsed. However, he very quickly realized that it was a local occurrence - only a few rooms and a hallway were affected - and, right in the center of it, was Danny, reading a book he borrowed (stolen) from the Wayne manor library.
The boy himself never noticed it. Which made sense, given that he defied gravity all on his own, always floating in the air above the floor.
But the others never acknowledged it either, treating the sudden absence of gravity as a sign of one, Danny appearing somewhere around, and two, him being in a good, if a bit absent, mood.
All in all, it's not the strangest thing that happens at the Watchtower on a daily basis.
And, besides, it's kind of fun.