Sudama was a childhood friend of Krishna. They attended their primary education in same school. But while Krishna was a royal prince, Sudama was born to a poor family. However, their financial differences didn't come in between their friendship. It is said that Sudama was the avatar of Lord Narada in order to see Krishna leela on earth. When they grew up, Krishna went on to become the royal king of Dwarka, where as Narada was confined to poor conditions in a village. Sometime later Sudama's financial conditions became even worse and he was not able to feed his family. At that time Sudama's wife reminded him of his childhood friend Krishna, and asked him to visit Lord and seek some help. A reluctant Sudama packed some rice with him as a gift, and took a long journey to reach Dwarka. Seeing his pity condition, at first the gate-keepers refused him entry to the city. When the news reached lord Krishna that Sudama has come, He became very joyful and rushed towards main gate to greet Sudama. Sudama was given a royal welcome. Lord Krishna even washed Sudama's dirty feet with His own hands. Krishna accepted the gift of Sudama graciously, which Sudama was trying to hide in order to hide shame. Due to Lord Krishna's grace, Sudama was offered uncountable wealth. When Sudama returned his village back, he was surprised to see that his small hut had turned into an huge palace! Jai Shri Krishna. Below are some wallpapers depicting this story.
(click on Krishna wallpaper to view large size)