Fanfiction-danny phantom & batman:Ectoplasmic Crystals by Clouds

Ectoplasmic Crystals
Clouds (myheadinthecoudsnotcomingdown)

Summary:
On the run from his parents, Danny has to find a way to block his ectosignature so he can stay hidden. The device he creates sure comes in handy when he's applying to an internship at Wayne Enterprises!

Basically, Kryptonite has an ectosignature and Danny figures out how to block it.

This is based off of the idea that Ectoplasm is the essence of death and a bit is released when a person died. When Krypton was destroyed, there was enough ectoplasm released that it soaked into the debris of the planet. Kryptonians are so affected because those rocks physically and supernaturally remind them of the death of their people and the possibility of their own deaths.