Originally Posted by
Timber Wolf-By-Night
Geoff Johns' attempt to shoehorn in an unknown and missing twin sibling of Lightning Lord's, from his brief run of stories about the LSH in Adventure Comics. Paul Levitz walked that aborted would-be plot back to the established status quo so not subtly, and so quickly. that you could practically hear him say out loud, "No, Geoff, that's a stupid idea."
The mid-90's Zatanna: Come Together mini-series and its long-term affects on Zatanna's character, costume, and powers. I actually liked it and understood the explanations and reasoning for the choices made in that mini that were given in the individual issues' text pieces, and was glad to see John Ostrander have that version of Zatanna make some appearances in his Spectre, so that story wasn't dropped quite as quickly as the OP was suggesting. But clearly, somebody (or several somebodies) behind the scenes at DC hated it, because some months after Zee's last guest-appearance in Spectre, she next appeared in the Superman titles, back in her half-tuxedo-half-fishnets costume, back to backwards-speaking spells, and back to being a stage magician, with the explanation being given in the letter's column afterwards when fans asked that Come Together had been completely retconned out of continuity. They didn't even try to come up with an in-universe explanation for reversing Zatanna's status quo.