User blog comment:Mercatorprojection/My Plans for the Wiki/@comment-24227188-20161117040437/@comment-27578229-20161119140228

Crossovers make people lazy due to already having characters and settings written out for you.

Crossovers between fanon on the wiki (take overgrowth for example) are usually okay because the two or more creators are working together and have their own set of characters. If you're taking characters from a well known series that has no affiliation with what you yourself are doing, then you already have their backgrounds, character, etc. set out and it's clear you've put no effort into 'extra cast'.