Sometimes, Their ankle bells tinkling, They (Krsna and Rama) would play football with fruits like bael and amalaki. Sometimes They would cover Themselves with blankets and imitate cows and bulls and fight with one another, roaring loudly - SB 10.11.39-40

Expressions researched:
"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"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

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.

SB 10.11.39-40, Translation and Purport

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.

Vṛndāvana is full of peacocks. Kūjat-kokila-haṁsa-sārasa-gaṇākīrṇe mayūrākule. The Vṛndāvana forest is always full of cuckoos, ducks, swans, peacocks, cranes and also monkeys, bulls and cows. So Kṛṣṇa and Balarāma used to imitate the sounds of these animals and enjoy sporting.