Every trouble in a child's life is the result of something. Sometimes, simple unawareness in the childish psychology could cause many uncured psychological complexes and troubles. Every children psychologist suggests that it is better to prevent than to cure.
Imagination
Of course, sometimes the adults are skillful daydreamers and cheaters due to their imagination and fantasy abilities, but usually this trouble is connected with the children's development. Imaginary situations are the logical result of the mind development. A child learns the world with the possible methods - gaming. If he/she tells you something which is not happening in the reality, it means that a kid is waiting for your reaction to learn. Ignorance is the worse thing you could do. Perhaps, a child tries to attract your attention or just communicate with you, but you are so busy with your work or something else that you deny an opportunity to check if the children's words are true. In the case of your ignorance a child used to repeat this trick again and again until he/she changes the family home for school, starts studying and the teachers point out this peculiarity of his/her. The kids who resort to the help of imagination to attract the parents' attention are to get more time with the parents to play, read a book before the bedtime, or create something together.
As a matter of fact, sometimes the friends could be imaginary as well, but it is to be overcome naturally. In some years a child learns how to deal with his/her imagination and live in the real world.