A Fat Chinese boy with a  goldfish refers to Golden Boy Jin Tong (fig.) saving the son of the Dragon King (fig.) in the form of a carp.

It is also a symbol for wealth in succession, because the character for ‘lotus’ is a homonym for the character for ‘successively’ and the word for fish is a homonym for the word for ‘surplus’, i.e. of gold (fig.), whilst being fat is a symbol of excess too.