Answer:
the looking-glass self
Step-by-step explanation:
According to the looking-glass self, a person will develop their identity according to how the society and the people in it perceive them.
In the example above, the child who are mediocre in every other aspects found a positive reactions that he decided to make jokes and play pranks.
The positive reaction will most likely him feel good about himself and he decided to form their identity as the 'funny one' in order to fit it with the rest of the group.