Solve Math Puzzle

An old man was sitting on a bench in the mall when a young man with spiked hair came over and sat down beside him. The boy's hair was yellow, green, orange, and purple. He had black makeup around his eyes. The old man just stared at him.
Finally the boy said, "what's the matter, old man, haven't you ever done anything wild in your life?"
The old man thought for a while and answered, "well yes actually, I have, I once got drunk and had sex with a parrot. I was just wondering if you were my son."