Why Brahma felt to krishan feet?
According to Krishna the Supreme Personality of God by A. C. Bhaktivedanta Swami Prabhupada
Story starts when Lord krishna after defeating Aghasura demon, Lord krishna was playing with his friends near yamuna river. Brahma knows that no ordinary person can defeat demon Aghasura. So Brahma wanted to test lord krishna as supreme God.
Moreover Lord brahma found shocking that krishna was playing in dirt and eating from there friends hand. According to lord brahma such behavior is not acceptable from God.
Lord brahma steals all calve and boys to his Brahamlok. Being supreme godhead krishna knows about brahma's plan. Krishna expand himself as exactly same calves and boys in same cloths . Mother of there child found some great affection towards their child. All were happy in village
When brahma return after one year to see the condition. He found shocking on seeing calves and boys were playing and enjoying. Because brahma knows that calves and boys were sleeping at brahamlok.
On seeing brahma confused. In order to convince Brahma that all those cows, calves and boys were not the original ones, the cows, calves, and boys who were playing with Krisna transformed into Vishnu forms.
After this manifestation of God Vishnu, Brahma saw that many other Brahmas and Shivas and demigods. Dancing on various music to worship lord vishnu. These brahma and shivas have different faces some have 100, 10000 or ever unlimited faces(According to this book vishnu is the creator of all brahma and shivas in multi universe )
After seeing this reality, Lord brahma return all calves and boys and felt to lotus feet of Shree Krishna.As these calves and boys were sleeping in brahma lok. They don't know anything happen. Lord krishna start playing with them.
Source: Krishna the Supreme Personality of God by A. C. Bhaktivedanta Swami Prabhupada(page 86-95)
Hare Krishna 
