Alphax said:
Agree with above. I think having a *very* obvious link to http://en.wikipedia.org/wiki/Wikipedia:General_disclaimer (with a section "Anything you see on April 1st could be a joke", or similar") would be a good idea.
Too broad. Just pop a datestamp at the top of the article and protect it from editing. The nonstandard appearance may also help to distinguish it from real articles.