Remember Medusa? - had a head full of snakes... well, she was only like that because virginal Athene caught her and Poseidon being naughty in her temple... so she cursed Medusa. Then, when dashing hero (ooh, I forget his name, was it Perseus?) cuts her head off, out springs Pegasus and a couple of other 'monsters'... who are all Poseidon's children, according to Greek ideas of conception.