From this answer by Keshav Srinivasan, Shishupala had three eyes and four arms.
When Shishupala was born, he had three eyes and four arms, which terrified his parents, the king and queen of Chedi.
Why he had these extra eye and arms?
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The story is mentioned in Mahabharata.
Bhishma said "Listen as I relate his history. Shishupala was born with four hands and three eyes, and upon his birth, he screamed like an ass. His parents were intently thinking of abandoning him for fear that he was a demon. Just when they were about to rid themselves of the child, a voice from the heavens spoke,'Do not abandon this child. He will prove to be a powerful warrior and will obtain all good fortune. He is not destined to die in his childhood. The person that will kill him has been born into this world already".
Bhishma continued, "Hearing the unembodied voice, the mother inquired, 'Who will be the slayer of my son?' The invisible being replied, 'The child will lose his two extra arms and eye when he is placed on the lap of a certain guest, and it will be that person who will slay your son.' Although the child was placed upon the lap of thousands of kings and princes, still the prophecy did not come true. One day Lord Krishna and Balarama came to the kingdom of the Chedis. They worshipped Their aunt and were given a fitting reception. When They took their seats, the queen brought the child to Krishna and placed it in His lap. The child immediately lost his two extra arms and the third eye. The queen in great anxiety then begged a benediction from Lord Krishna, 'O mighty armed Krishna, please grant me that You will excuse the offences of my son Shishupala.' Lord Krishna replied, 'O my aunt, I say that I will pardon one hundred offences committed by your son. Do not grieve for his life.'