"Sometimes Kṛṣṇa and Balarāma would play on Their flutes, sometimes They would throw ropes and stones devised for getting fruits from the trees, sometimes They would throw only stones, and sometimes, Their ankle bells tinkling, They would play football with fruits like bael and āmalakī. Sometimes They would cover Themselves with blankets and imitate cows and bulls and fight with one another, roaring loudly, and sometimes They would imitate the voices of the animals. In this way They enjoyed sporting, exactly like two ordinary human children."
- Śrīmad Bhāgavatam 10.11.39-40
This is Rama and Krsna's sesa kumara lila. By this time they have been weened from their mothers' breast milk, the spontaneous flowing of which is a special sattvika-bhava in vatsalya-rasa. Thus at this period they move away from being "mothers' boys" and, for example, try to dress themselves. They have only recently taken up residence in Vrindavan and their ambition is to herd cows. Receiving the blessing to herd calved they are equipped with flutes, buffalo horns, ropes, and sticks. At this time the Vrindavan forest is overwhelmed with at the prospect of being blessed by their lotus feet.
This sesa kumara lila is the beginning of the conflict between vatsalya and sakhya rasa. It is the budding of Krsna's antahkarana that is permeated by sakhya rasa. That antahkarana will flower and begin to bear the fruit of who he is in the middle of his pauganda lila when he looks sideways at the gopikas. It will mature in his kishore lila.
At this age the sight of the Krsna, whose waist has thinned on its own and whose chest seems to have suddenly broadened, stuns his mother.