According to the Mythology, Lord Ganeshas vahan i.e Mouse was a Gandharva who was a celestial singer in his previous birth, named Kroncha, in the court of Indra Dev. One day, Kroncha insulted sage Vaamedeva. And the sage got angry and cursed him to become a mouse. Krauncha forgot his role as a musician and derived all the characteristics of a mouse.
He went to the ashram of sage Paraashara and created despoliation. This interrupted the peace of the ashram and the helpless sage prayed to Lord Ganesha. His unrivaled and earnest reverence elated and he brought the mouse under his control. And this is how Lord Ganesha had his vahan in the form of mouse.
It is believed that the mouse is a symbol of all pervasive omniscient
Brahman. As it is considered as the creature of the dark underground, he
travels all under the ground where nobody can reach. It is a symbol of
ignorance that fears light and knowledge.
