Mahārāja Parīkṣit, the grandson of the Pāṇḍavas, was from his very childhood a great devotee of the Lord. Even while playing with dolls, he used to worship Lord Kṛṣṇa by imitating the worship of the family Deity.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
स वै भागवतो राजा पाण्डवेयो महारथः । बालक्रीडनकैः क्रीडन् कृष्णक्रीडां य आददे
sa vai bhāgavato rājā pāṇḍaveyo mahārathaḥ | bālakrīḍanakaiḥ krīḍan kṛṣṇakrīḍāṃ ya ādade
SB 2.3.15