He was used to being made fun of.
We know this by him taking this reply in ‘with a sort of humble patience’. This means that he has experienced this kind of teasing - or even bullying before and he is used to it.
Plot-driven stories place a larger emphasis on the actual plot itself. Factors such as plot twists, action and external conflict are what make up the focus of this style of writing.
The event which shows the monster has gained his humanity by the end of the story is his weeping over Victor Frankenstein's dead body. The man who had created him had denied him the right to enjoy the love of a wife and family, and now it was too late.
I’m thinking giggles. Since it is a birthday party.