What April Fools Tricks Should I Play?

Well there are millions, and it can be a lot of fun, just remember not to upset anyone to severely, or to do anything that can bring them harm. The rule is, would I be able to laugh at this, if it was me. Don't do anything to others, that you wouldn't want  done to you, is the golden rule.
So, with that in mind, you could ring  up, and ask them if their fridge is running, and when they check and then come back and tell you it is ok the power is on it is running,  then,you say, "Well you better catch it then, it is running out the door",  roar with laughter, and put the phone down.
Silly , stupid, but we used to get hours of fun from this one, as children.
Then the was the time I told my partner I had lost all the files on our computer, because I did not do back up. He was so concerned, I could not hold the secret, and after ten minutes of his frantic pacing, had to put him out of his misery, as I felt so sorry for him.
A friend of mine once rang up her arrogant, pompous boyfriend, who had taken his much beloved car into the panelbeaters for a small touch up. On the day he was to finally collect it. She rang him, posing as the secretary from the panel beater,  and  she said,  "Unfortunately, one of the new mechanics has put your car though the wall, when he drove it out without permission." There was silence, then he went  completly crazy, and nearly swallowed his own head. So I don't suggest that one either.
Be nice!