When Lord Krishna went ahead to a distant place in order to see some specific scenery, the boys behind Him tried to run to catch up and be the first to touch Him. So there was a great competition. One would say, "I will go there and touch Krishna," and another would say, "Oh you cannot go. I'll touch Krishna first." Some of them played on their flutes or vibrated bugles made of buffalo horn. Some of them gladly followed the peacocks and imitated the onomatopoetic sounds of the cuckoo. While the birds were flying in the sky, the boys ran after the birds' shadows along the ground and tried to follow their exact courses. Some of them went to the monkeys and silently sat down beside them, and some of them imitated the dancing of the peacocks. Some of them caught the tails of the monkeys and played with them, and when the monkeys jumped in a tree, the boys also followed. When a monkey showed its face and teeth, a boy imitated and showed his teeth to the monkey. Some of the boys played with the frogs on the bank of the Yamuna, and when, out of fear, the frogs jumped into the water, the boys immediately dove in after them, and they would come out of the water when they saw their own shadows and stand imitating, making caricatures and laughing. They would also go to an empty well and make loud sounds, and when the echo came back, they would call it ill names and laugh.
The demon Aghasura appeared before Krishna and His friends. Aghasura happened to be the younger brother of Putana and Bakasura, and he thought, "Krishna has killed my brother and sister. Now I shall kill Him along with all His friends and calves." Aghasura was instigated by Kamsa, so he had come with determination. Aghasura also began to think that when he would offer grains and water in memory of his brother and kill Krishna and all the cowherd boys, then automatically all the inhabitants of Vrndavana would die. Generally, for the householders, the children are the life and breath force. When all the children die, then naturally the parents also die on account of strong affection for them.
The demon in the shape of a big fat serpent expanded his lips from the land to the sky; his lower lip was touching the ground and his upper lip was touching the clouds. His jaws appeared like a big mountain cave, without limitation, and his teeth appeared just like mountain summits. His tongue appeared to be a broad traffic way, and he was breathing just like a hurricane. The fire of his eyes was blazing. At first the boys thought that the demon was a statue, but after examining it, they saw it was more like a big serpent lying down in the road and widening his mouth. The boys began to talk among themselves: "This figure appears to be a great animal, and he is sitting in such a posture just to swallow us all. Just see -- is it not a big snake that has widened his mouth to eat all of us?"
One of them said, "Yes, what you say is true. This animal's upper lip appears to be just like the sunshine, and its lower lip is just like the reflection of red sunshine on the ground. Dear friends, just look to the right and left hand side of the mouth of the animal. Its mouth appears to be like a mountain cave, and its height cannot be estimated. The chin is also raised like a mountain summit. That long highway appears to be its tongue, and inside the mouth is as dark as in a mountain cave. The hot wind that is blowing like a hurricane is his breathing, and the fishy bad smell coming out from his mouth is the smell of his intestines."
Then they further consulted amongst themselves: "If we all at one time entered into the mouth of this great serpent, how could it possibly swallow all of us? And even if it were to swallow all of us at once, it could not swallow Krishna. Krishna will immediately kill him, as He did Bakasura." Talking in this way, all the boys looked at the beautiful lotus-like face of Krishna, and they began to clap and smile. And so they marched forward and entered the mouth of the gigantic serpent.
Krishna is the assurance of safety to everyone. But when He saw that His friends were already out of His hands and were lying within the belly of a giant serpent, He became, momentarily, aggrieved. He was also struck with wonder how the external energy works so wonderfully. He then began to consider how the demon should be killed and how He could save the boys and calves. Although there was no factual concern on Krishna's part, He was thinking like that. Finally, after some deliberation, He also entered the mouth of the demon. When Krishna entered, all the demigods, who had gathered to see the fun and who were hiding within the clouds, began to express had also entered the mouth of the demon.
When Lord Brahma heard those auspicious vibrations which sounded throughout the higher planetary system, he immediately came down to see what had happened. He saw that the demon was killed, and he was struck with wonder at the uncommon glorious pastimes of the Personality of Godhead. The gigantic mouth of the demon remained in an open position for many days and gradually dried up; it remained a spot of pleasure pastimes for all the cowherd boys
For Sri Krishna, the Supreme Personality of Godhead, who is far greater than such demigods as Lord Brahma, it is not at all difficult to award one the opportunity of merging with His eternal body. This He awarded to Aghasura. Aghasura was certainly the most sinful living entity, and it is not possible for the sinful to merge into the existence of the Absolute Truth. But in this particular case, because Krishna entered into Aghasura's body, the demon became fully cleansed of all sinful reaction. (from Krishna Book by His Divine Grace A.C. Bhaktivedanta Swami Prabhupada.)