I have to admit then when I was a kid I used to be involved in some random calls to people I didn't know.
We would say and do stupid things simply to amuse ourselves.
Not only is this immoral, it's not very funny either! However many people who started like me now make part of their livelihood from calling people in a funny way and broadcasting the funny results on radio/television or the internet.
Done in the right, respectful way these funny prank calls are nothing short of pure hilarity! Well if you want to start making funny calls then you have the internet at your disposal to show off your calls.
You may be a great impersonator or just enjoy the fun of it.
You could call up friends and publish the calls with their approval or even try straight for famous people! Here is are a few tip for successfully pulling off a funny prank call.

1. Plan a script as best as you can.
   
2. Write down the phone numbers, names and anything important.
   
3. Don't plan to insult the person.
   
4. Always test your recording equipment before the big call.
   
5. Maybe before going for the big guns it's worth honing your skills on a few friends.
   
6. Always reveal the prank at the end of the call.
   
7. Get written permission before publishing a call.
   

This is by no means a comprehensive list, just some ideas to get you going, do your research, get some good scripts, be respectful and have some fun.
The world is waiting!