In the interest of that not happening AGAIN, I present to you...
--THE BIG OL' LIST OF APRIL FOOL'S RULES--
(Keeping you from being too foolish)
1: No false "I'm leaving the site" jokes.
2: No jokes that abuse mod/admin powers.
3: This includes the chat.
4: Try to keep the jokes lighthearted if you must make them.
5: Sgt. Porter is best navi.
6: April fools! There is no 6th rule.
7: Just generally try to use common sense for your jokes. Does it hurt or inconvenience someone else? Then it's a bad joke. Could it be taken seriously? Then it's a bad joke. Is it offensive AND hurtful (IE: "Guys there's a second Tsunami headed for Japan!")? Then it's a REALLY bad joke and you should feel bad.
Keep all these in mind when planning and executing your pranks, and we'll all have a happier time for it.