I don't know about craziest but I've done a few surprise birthdays and weddings, the best was the bride of a fellow member (a stormtrooper) contacted us without him knowing and asked for us to make an appearance at their wedding, the member knew nothing until we came charging out when we heard "does anyone have any reason why these two should not be wed" to which we replied "stop, stop your wanted back on the death star" got a roar of laughs and the member was really chuffed, he couldn't stop thanking us after the event.