Today is April Fools day, the day the many people like to play pranks or tricks on people, and then say, "April Fools!" The perceived expectation is that saying "April Fools" after playing a trick will make the Prank OK. However some people like to play hurtful jokes, such as, "I want a divorce" while handing the target a supposed divorce papers. This is a cruel type of emotional prank. Another type of prank might to be set something up so that the target person unknowning does something that triggers a physical disaster to happen or a mess to made. This is another type of cruel joke.
When playing a joke on someone it should only be something that the victim will think is funny.