Originally, when Mickey first meets him in his dream, he was reviled to be friendly at first when he invites him into the mirror. Then later, he turns out to be greety and evil and would pick on Mickey, tease and play tricks on him were ever room and area he goes too. Towards the end of the game, he reformes, his personaly changes and it was revieled why he invided Mickey into the mirror because he only wanted a friend to play with, he then becomes kind and friendly when Mickey invites him to come home with Mickey to his room.
In the game, he invites Mickey Mouse to come inside the mirror to go exploring. When Mickey goes to the next room and finds the mirror that leads back home, the Ghost appears on the other side and scares Mickey. He then uses his electrical powers to destroy all the glass in the mirror and prevented Mickey from escaping. He then spreads all the glass pieces through all the areas and rooms inside the mirror, were it was up to Mickey to find all of them. At times, he will play tricks on Mickey or just scare him. He reforms in the end when Mickey invites him to come home with him to his room, and later on, he becomes good friends with Mickey.
But if the player dosn't collect all the pieces and only finds 8 pieces, the Ghost won't be able to go home with him.