You do not need to restrict yourself to April fools' day to play a practical joke on someone. If you want to play a prank on someone, one of the best and time tested ways to go about it is to make a prank call. These are a lot of fun, and can be the source of much amusement.
The point of using one of these ideas for joke calls to have a hearty laugh. Do ensure that you do not take these funny pranks beyond a limit, as you do not want to cause trouble for the person you are playing the prank on.
Now ask a vague and stupid yet embarrassingly personal question. If they do answer the question, take their name and address down and then tell them that this was for a radio show on game shows and that it has been broadcast as they were talking to you. This should elicit some great response.
Change your voice every time you call them. In the evening, call up the person you are playing the prank on again and say, "Hello, I am (the person you have been asking for the entire day). Do you have any messages for me."
Be careful of using this idea though, as you do not want to cause too much trouble. Clear the air as soon as possible.
☎ Mimic the person you are placing the prank call on and repeat everything that he or she says. This is one of the best ideas that you can use. If they say, hello, repeat the same, if they say, are you mad, you do the same.
☎ If you want to get back at someone who always pranks you, then play this. Call the person and say, "Hello, this is the police department. There have been several reports that have been filed against you for making prank calls to innocent and law-abiding citizens. This is a nuisance to them and if you do not stop this right now, you will be fined $500."
Ask them to pass on the message and collect the same from the front desk when he visits them next. This should lead to some pretty interesting situations. This is not exactly one of the harmless practical jokes that you can play, so be sure that the people you are playing the prank on can laugh at themselves.
These are just some of the ideas that you can opt for, if you want to make some prank calls. Good pranks are generally those that you have come up with yourself. Using cliched ideas can, at times, fall flat. So give an interesting twist to any idea that you use. Make that call and have fun laughing your heart out.