User blog comment:Nan the cowdog/A important message from Nan (READ)/@comment-1647442-20141207184701

Direct from the policy listing:

"In addition, if one chooses to crossover with another series, any characters from that series mustn't have an article. For example, if you made a Futurama crossover, you shouldn't make an article about Leela on here. If there is a Futurama Fanon Wiki, well, you could add the story onto there as well, and add the information onto Leela's Futurama Fanon article, and interwiki link them."