There is a nice statement in the Kūrma Purāṇa about these contradictory traits of the Supreme Personality of Godhead. It is stated there that the Supreme Person is neither very fat nor very thin; He is always transcendental to material qualities, and yet His bodily luster is blackish. His eyes are reddish, He is all-powerful, and He is equipped with all different kinds of opulences. Contradictory traits in Kṛṣṇa's person are not at all surprising: one should not consider the characteristics of Kṛṣṇa, the Supreme Personality of Godhead, to be actually contradictory. One should try to understand the traits of Kṛṣṇa from authorities and try to understand how these characteristics are employed by the supreme will of the Lord.
In the Mahā-varāha Purāṇa it is confirmed that the transcendental bodies of the Supreme Personality of Godhead and His expansions are all existing eternally. Such bodies are never material and are completely spiritual and full of knowledge. They are reservoirs of all transcendental qualities. In the Vaiṣṇava Tantra there is a statement that the Personality of Godhead and His expanded bodies are always free from the eighteen kinds of material contaminations,* because such bodies are always full of knowledge, bliss and eternity.
Regarding all of the above-mentioned statements, it is understood that the Mahā-Viṣṇu is the source of all incarnations in the material world. But because of His greater extraordinary opulence, we can understand that the son of Nanda Mahārāj is the source of the Mahā-Viṣṇu also. This is confirmed in the Brahma-saṁhitā, wherein it is stated: "Let me offer my respectful obeisances unto Govinda, whose partial representation is the Mahā-Viṣṇu." The gigantic form of the Mahā-Viṣṇu is the source of generation for innumerable universes. Innumerable universes are coming out of His exhaling breath, and the same universes are going back in with His inhaling breath. This Mahā-Viṣṇu is also a plenary portion of a portion of Kṛṣṇa.