The shinanigans of Friday the 13th were not a prank, rather Aku's way of saying "Hi," on one of his favorite days. No one was worried like with April Fools, but there were still those bothered by his visit.
Spongey34 originally had the idea for some harmless fun, and carterhawk quickly took care of things. Once again, he can be thanked for all the drastic changes. Also noe that this time Aku was played by just carter, and not the whole staff.
So, mark your calendars for next Friday the 13th. And for those of you who didn't believe, maybe know you will. Remember to watch out for those mirrors, broken glass, black cats, ladders, and Cartoon Network characters.