A poor man has very little to eat so is thin and frail. A worker labours hard for a living so is sinewy and muscular. A rich man is plump and well-endowed because he neither sweats in the field nor ever goes hungry.
So observed the early forefathers within their thriving, bustling grass-root societies and concluded if there ever was a god of wealth, a huge fat pot belly would have to be an important part of his description – and thus came about Kubera, the Hindu lord of wealth who since the time of his creation evolved and changed, both in form and story, as one generation gave away to the next, yet never lost his trademark lumpish, roundish shape.
The master sculptors of Mathura of the Kushan period did not invent Kuber or his legends. By the time Kuber reached their studios, he was already a deity in his own right and well entrenched in Indian mythology, having found a place in the great Indian epics of Ramayana and Mahabarata.
What the sculptors merely did was add in little nuances to his divinely obese stature like a flock of curly hair, a moustache and a robe that revealed their times, fashion and taste. Furthermore, they chipped away his earlier image of a hideous old man with three legs and eight teeth, as mentioned in the old Puranas, and brought in a uniformity, later to be reproduced with little changes by different cultures and religions that adopted him.
Like the Gandharan Buddha (see Farbound.Net snippet: the Greek Buddha), the statue of Kubera is a unique work of art, and was possibly one of the earliest to be produced, modelled after a Kushan nobleman.

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The Kushans, who were originally a nomadic clan of horse archers, ruled vast stretches of the Indian subcontinent between the 1st and 5th century C.E. Reigning from their two capital cities located at Taxila and Mathura, the Kushan kings, being great patrons of art and craft, had encouraged sculpting which had led to the establishment of two separate schools. One at Gandhara (present-day Pakistan and Afghanistan) and the other at Mathura (present-day state of Uttar Pradesh, India).
Both regions were instrumental in introducing innovations in the field simultaneously, but had done so in their own distinctive way. While the art of Gandhara reflected Greek influences, Mathura was more local in form and outlasted its contemporary.
In present-day India, Kubera is still worshipped in spite of the huge popularity of Lakshmi, the goddess of wealth. Though he still remains a lesser god, as during the time of the Puranas.