Vrndavana dasa Thakura is Lord Nityananda's favorite devotee
Sri Caitanya-caritamrta
CC Antya-lila
Vṛndāvana dāsa Ṭhākura is Lord Nityānanda's favorite devotee, and therefore he is the original Vyāsadeva in describing the pastimes of Śrī Caitanya Mahāprabhu.
Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura says that all writers after Vṛndāvana dāsa Ṭhākura who are pure devotees of Śrī Caitanya Mahāprabhu and who have tried to describe the Lord's activities are to be considered like Vyāsa. Śrīla Vṛndāvana dāsa Ṭhākura is the original Vyāsadeva in describing caitanya-līlā, and all others who follow in his footsteps by describing Śrī Caitanya Mahāprabhu's pastimes are also to be called Vyāsadeva. The bona fide spiritual master is called Vyāsa because he is a representative of Vyāsa. Worshiping the birthday of such a spiritual master is called Vyāsa-pūjā.