AU where the justice leauge creates a dimensional hopper to grab other versions of themselves in times of severe need by putting in DNA that then grabs the closest match from a given universe
They need to test it amd decide to use Nightwing's DNA because they figure he is the least likely to have an entirely evil alternate self, and they put it in and input a universe at complete random- Earth 199999 (because the MCU is NOT 616 fight me Feige) and out pops Spider-Man because he is that universes closest (alive) genetic match
Cue confusion as the JL tries to figure out why Nighwing is obviously younger, and has a completly different costume and accent and why he doesn't recognize anything until Nightwing takes his mask off and before he can even introduce himself, the entire room is stunned into silence by a choked "Dad?"
