It has everything. Here's some proof:
This fanfic is about Uchiha Itachi (Naruto) fighting the cast of O.C. with an army of clones. Important to the plot: The Frozen Fire.
This fanfic is about Mr. K (Gravitation) trying to kill J. Jonah Jameson (Spider-Man).
This fanfic is about Patrick Harper (Sharpe) shopping with Angelo Espinosa (X-Men). Miss Scarlet (Clue) helps out with a donation of money.