The vehicle of Lord Ganesha is a mouse, called Mooshik or Munjoor.

Each vahan (or vehicle) in Hinduism symbolises a specific characteristic which also goes with the deity. Logically a small mouse can't carry a deity with a large body such as Lord Ganesha, but that is where the symbolism takes its importance.

"The basic characteristic of a mouse is its greediness - mice tend to eat whatever it comes across. They bite or nibble at anything, thereby rendering it unusable for others."

By having a mouse as HIS vehicle, Lord Ganesha tells us the most important characteristic that we should learn to control - greed.

We should:

1
Take only what's necessary for us.
2
Control your desire
3
Bite in, only when we are hungry.
4
Not waste food.
5
Not peep into others' lives.