Anyways, when looking up that Perseus stuff, I found this...
Cerberus is one of the offspring of Typhoeus and Echidna. It is a three headed dog with a snake tail and snake heads proturding from his back. He guards the entrance to the underworld, allowing the dead to enter but, never to leave. One of the few living mortals to get past Cerberus was Orpheus who charmed it to sleep with his song during his attempt to rescue Eurydice from death. Fetching Cerberus from the underworld and displaying him to King Eurystheus was the last labor of Heracles .
Now, I know it's not identical, butn otice the similarities to Fluffy! I'm wondering exactly how much effort JK puti nto these books, because as I was going through the page *it had a whole list of greek mythology creatures and other stuff* I found other creatures, very similar to some of those in 'Fantastic Beasts and Where to Find Them'.
I think it's jsut phenomonal the amount of work JK put in... either that or she is one lucky guesser!!! hehehe!