Devibhagavatapurana 4.2.36

4.2.36

rāmāvatārayogena devā vānaratāṃ gatāḥ |
tathā kṛṣṇasahāyārthaṃ devā yādavatāṃ gatāḥ ||

In the Rama Incarnation, the Devas had to incarnate themselves a Monkeys; and in the Krisna incarnation, the Devas had to incarnate themselves as human beings, Cow-herds (Gopas) and Yâdavas.