Preparation: You need to prepare a gimmick. Cut a spoon head of an old spoon. I prefer that you do it with a plastic spoon before a metal one because cutting off a metal spoon head needs a lot of hardwork and help from adults.

Secret: You place the gimmick right behind the spoons head. Fix it in such a way that it looks as if you are a holding a single spoon.
Performance: Now, I have told you the secret , probably its understood how to do the trick. Well, you hold the spoon in such a way that yuor thumb covers the edge of the gimmick. In this way no one can ever notice that you are holding a gimmick behind. It can be held in any way that you feel comfortable with. Then, tell everyone that you are going to something very unusual with the spoon. You can even say that "oh!this spoon only has one head. It would have been much easier to eat if it had two"
Then you slide the gimmick behind. Don't show it for too long but slide it back quickly before the audience figures out how did it. If you like you can add one more gimmick behind to create a three head illusion.
Also, when you are sliding the gimmick back try to cover it up with your other hand as if you are telling the spoon to have one head. This helps the you to fix the gimmick properly.
Sliding the gimmick needs a little practice but the rest of the trick is a piece of cake!!!!
It may look simple but has a great effect on the audience!!!
Go on! What are you waiting for!!
FREAK EVERYONE OUT!!!