rusty_halos has written a very cool Trinity story for the 2012 DCU Fic/Art Halloween Challenge. It's a crossover with Harry Potter and is a real page-turner! :)
BradyGirl_12 DCU Challenges A03 Collection
The complete Master List is here.
Title: The Absolute Worst Halloween Ever (According to Bruce Wayne, Clark Kent, Diana Prince, and Pretty Much Everyone Else at the Hogwarts School of Witchcraft and Wizardry)
Genre: Friendship/family, fluff, drama
Pairing: Superbats pre-slash, but genfic if you don't feel like using your slashy lenses.
Summary: Bruce and his best friends Clark and Diana are just normal seventh years at Hogwarts, dealing with Transfiguration exams and magical mishaps, House rivalries and inappropriate romances. At least, as normal as a Pureblood scion, a superpowered Muggle, and an Amazon princess out to explore wizard's world could possibly be. Add in Slytherins like Luthor and an alien god who could make Voldemort wet his pants, and it's a recipe for the Worst. Halloween. Ever.
DCU crossover with Harry Potter, written for the dcu_freeforall Autumn Challenge (T16; P34: Fall/Autumn), bradygirl_12's Halloween challenge (witches, books on magic, ritual, wants, cloaks, Harry Potter), and the prompt "fantasy" from my Superbats challenge table.