It is rude to misbehave at a family funciton.
Dewey is a child and his family is at a wedding for his aunt.
Dewey wants to have fun.
Dewey uses his imagination to pretend he is somewhere else during the ceremony and is on a grand adventure.
Dewey gets up and starts to dance and sing right in the middle of the ceremony part of the wedding.
Dewey enjoys himself and before he knows it the ceremony is over, and he is eating cake at the reception.
Dewey gets in trouble and is punished for weeks on end.