Whomever is doing this is seriously immature, sure it is funny but they know they can just make their own joke wiki or something instead of trolling wiki pages used for getting more info about a certain character and such.
I'm seeing this crap constantly. Personally I don't find it funny and Keiji's page idk how to return it back to the way it was before because someone messed with it. I changed Sara's and idk if Joe's was changed or not?
I believe you can go into the history of a page (top right corner of any given page) and revert it, but I can't remember if that's something only admins have the power to do.