Krsna displayed His real four-armed form
Bhagavad-gita As It Is
BG Chapters 7 - 12
BG 11.50, Translation: Sañjaya said to Dhṛtarāṣṭra: The Supreme Personality of Godhead, Kṛṣṇa, having spoken thus to Arjuna, displayed His real four-armed form and at last showed His two-armed form, thus encouraging the fearful Arjuna.