You will find in Caitanya-caritāmṛta, it is quoted from Śrīmad-Bhāgavatam that one sometimes . . . it is called līlā, pastime, that Brahmā, when Kṛṣṇa was here on this planet, so Brahmā was very much proud that "Kṛṣṇa is now in the earthly planet, and this earthly planet is one of the innumerable planets under my control." Brahmā is the controller, is the primal, principal living entity in this universe, so he was little proud that "Kṛṣṇa is within my control."
So therefore Kṛṣṇa, because He is Paramātmā, He knows everything, what one thinks, what one does. So He, Kṛṣṇa, asked Brahmā to come and see Him. So Brahmā came. Brahmā came. His doorman informed Kṛṣṇa that . . . time doorman asked Brahmā, "Who are you, please?" "Now, you say Kṛṣṇa that I am Brahmā. I have come to see Him." So when the doorman informed Kṛṣṇa that—in Dvārakā, when Kṛṣṇa was there as king—so Kṛṣṇa asked, "Oh, which Brahmā? Which Brahmā?" The doorman came back again and informed that "Which Brahmā you are?"
So Brahmā became astonished, " 'Which Brahmā?' And I am the Brahmā. I am the supreme creature within this universe, and 'Which Brahmā?' " He was surprised, and he said, "Tell Kṛṣṇa that four-headed Brahmā." Brahmā has four head. So Kṛṣṇa called him, "All right, come on." So he came, and he offered his obeisances, and Brahmā asked Him, "Kṛṣṇa, my dear . . . my Lord, may I ask You some question?" "What is that?" "That Your doorman asked me, 'Which Brahmā?' So does it mean there are other Brahmā also?" Oh Kṛṣṇa said: "Yes, there are innumerable Brahmās. You are only four-headed. There are eight-headed, there are sixteen-headed, thirty-two–headed, sixty-four–headed, hundred-twenty-eight–headed, and millions of headed. So all right, I am calling them all."